Weapons of Mass Destruction Counterproliferation: Legal Issues for Ships and Aircraft

CRS Report for Congress
Weapons of Mass Destruction
Legal Issues for Ships and Aircraft
October 1, 2003
Jennifer K. Elsea
Legislative Attorney
American Law Division

Congressional Research Service ˜ The Library of Congress

Weapons of Mass Destruction Counterproliferation:
Legal Issues for Ships and Aircraft
President Bush outlined a specific plan to counter WMD proliferation in his
National Strategy to Combat Weapons of Mass Destruction of December, 2002. The
Administration’s plan combines efforts aimed at counterproliferation,
nonproliferation, and WMD consequence management. The intent, it says, is to
eliminate or “roll back” WMD in the possession of certain States and terrorist
groups, including potentially the use of force and aggressive methods of interdiction
of WMD-related goods, technologies, and expertise. The use of interdiction as a
counterproliferation measure appears to be part of a strategy that foresees the U.S.
taking “anticipatory action to defend ourselves” against terrorists and rogue States,
“even if uncertainty remains as to the time and place of the enemy’s attack,” and “to
detect and destroy an adversary’s WMD assets before these weapons are used.” A
recent refinement of the WMD strategy is the Proliferation Security Initiative (PSI),
which would involve cooperation among friendly nations to interdict transfers of
restricted weapons and related technologies “at sea, in the air, and on land.”
However, the Administration has recognized that cooperation may not always be
forthcoming, and has intimated that it will act unilaterally, if necessary.
Aspects of this national security strategy raise questions related to the
international law of jurisdiction, the law of the sea (which also references airspace),
and international civil aviation agreements. The right of States to conduct self-
defense and law enforcement activities abroad has the potential to collide with the
rights of other States to maintain their sovereign integrity and conduct free navigation
and commerce. These rights are not absolute. This report provides an overview of
the international law of the sea and other agreements as they relate to the permissible
range of methods for interdicting WMD-related contraband. After a short summary
of the current legal regime for international arms control related to WMD, the report
outlines the basic concepts of jurisdiction in international law. Next, the report
describes concepts central to the law of the sea, including the division of the world’s
waters and airspace into “international” and “national” territory, and a description of
the rights, duties and limitations that apply depending on where the conduct takes
place. The report then turns to the international legal framework limiting the conduct
of nations as it applies during times of war and peace, and during what has been
called “quasi war.”

In troduction ......................................................1
Weapons of Mass Destruction – International Legal Regime................3
Nuclear Weapons..............................................4
Chemical Weapons............................................6
Biological Weapons ...........................................7
Limitation on Enforcement......................................8
Jurisdiction under International Law...................................8
The Law of the Sea...............................................10
Legal Divisions of Waters......................................11
Territorial Seas...........................................11
Contiguous Zones and Exclusive Economic Zones (EEZ).........12
Straits ..................................................13
The High Seas...........................................13
Legal Status of Vessels........................................13
Nationality ..............................................14
Status of Warships........................................14
Airspace and Aircraft..........................................14
Law of the Sea Conventions................................15
Chicago Convention.......................................15
Nationality of Aircraft.....................................16
State Aircraft............................................17
Enforcement Options..............................................17
Law Enforcement in National Waters and Airspace..................17
Law Enforcement on the High Seas...............................18
Unlawful Acts on the High Seas.............................18
Right of Approach and Visit................................19
Enforcement Measures.....................................19
The Proliferation Security Initiative...............................21
Belligerent Rights............................................23
The Right of Visit and Search...............................24
Naval Blockades.........................................24
Air Blockade............................................25
Blurring the Boundary between War and Peace.....................25
The Right of Self Defense..................................25
Pacific Blockade.........................................26
Self-help Paradigm in International Law.......................27
Collective Action Under Security Council Mandate..............32
Conclusion ......................................................33
Appendix A – Interdiction Principles for the Proliferation Security Initiative..35

Weapons of Mass Destruction
Legal Issues for Ships and Aircraft
After the collapse of the Soviet Union, the world’s security landscape is said
to have undergone a transformation from the seeming stability of the bi-polar balance
of power to a system in which not only any nation, but sub-national groups as well,
may be able to acquire weapons of mass destruction (WMD). Strategies based on
containment and deterrence, it is argued, are insufficient to guarantee security in the
twenty-first century threat environment; terrorists and “rogue” nations are not
amenable to being deterred or contained.1 The need to prevent the proliferation of
chemical, biological, and nuclear weapons was highlighted in the National Security
Strategy of the United States of America issued in September, 2002.2 According to
the Bush Administration, in order to strengthen nonproliferation efforts to prevent
rogue States and terrorists from acquiring weapons of mass destruction,
[w]e will enhance diplomacy, arms control, multilateral export controls, and
threat reduction assistance that impede states and terrorists seeking WMD, and3
when necessary, interdict enabling technologies and materials.
Toward that end, President Bush issued his National Strategy to Combat
Weapons of Mass Destruction in December, 2002. The Administration’s plan
combines efforts aimed at counterproliferation,4 nonproliferation, and WMD
consequence management. Its purported intent is to eliminate or “roll back” WMD
from certain states and terrorist groups who possess such weapons or are close to

1See Michael N. Schmitt, Preemptive Strategies in International Law, 24 MICH. J. INT'L L.
513, 515-18 (2003) (describing the Bush Administration’s assessment of national security
priorities) .
2White House, The National Security Strategy of the United States of America (September,

2002)[hereinafter “NSS”], available at [http://www.whitehouse.gov/nsc/ nss.html].

3Id. at 14.
4See White House, National Strategy To Combat Weapons of Mass Destruction 2
(December, 2002) [hereinafter “WMD Strategy”] available at
[http://www.whitehouse.gov/news/releases/2002/12/WMDStrategy.pdf], noting that
[e]ffective interdiction is a critical part of the U.S. strategy to combat WMD and their
delivery means. We must enhance the capabilities of our military, intelligence, technical,
and law enforcement communities to prevent the movement of WMD materials,
technology, and expertise to hostile states and terrorist organizations.

acquiring them, including potentially the use of force and aggressive methods of
interdiction of WMD-related goods, technologies, and expertise.5 The use of
interdiction as a counterproliferation measure appears to be part of a strategy that
foresees the U.S. taking “anticipatory action to defend ourselves” against terrorists
and rogue states, “even if uncertainty remains as to the time and place of the enemy’s
attack,”6 and “to detect and destroy an adversary’s WMD assets before these weapons
are used.”7
A high-profile incident involving the interception of Scud missiles and rocket
fuel on board a ship traveling from North Korea in December, 2002, however,
illustrated possible legal impediments to the strategy. Acting on intelligence from
the United States, a Spanish frigate stopped and boarded the So San, an unmarked
North Korean commercial vessel, and discovered the missiles. However, after
confirming that the missiles were purchased by Yemen, the United States allowed the
vessel to proceed on its voyage. The Bush Administration concluded that there was
no legal basis to arrest the vessel or seize its cargo, because North Korea had not
violated any law.8
In May 2003, President Bush announced a new facet of the WMD strategy, to
be known as the Proliferation Security Initiative (PSI).9 The PSI is an effort to reach
agreements among nations to allow searches of ships and aircraft carrying suspected
weapons-related cargo.10 Undersecretary of State for Arms Control and International
Security John Bolton told Congress:
The initiative reflects the need for a more dynamic active approach to the global
proliferation problem. It envisions partnerships of states working in concert,
employing their national capabilities to develop a broad range of legal,
diplomatic, economic, military and other tools to interdict threatening shipments
of WMD and missile related equipment and technologies.
To jump-start this initiative, we have begun working with several close allies and
friends to expand our ability to stop and seize suspected WMD transfers. Over
time we will extend this partnership as broadly as possible to keep the world's
most destructive weapons away from our shores and out of the hands of our
enemies. We aim ultimately, not just to prevent the spread of weapons of mass

5See NSS, supra note 2, at 21.
6Id. at 15.
7WMD Strategy, supra note 4, at 3.
8See Ari Fleischer, White House Press Briefing, Dec. 11, 2002, available online at 2002 WL

31764110 (F.D.C.H.)(Westlaw).

9President George W. Bush, Remarks to the People of Poland (May 31, 2003), available at
[http://www.whitehouse.gov/news/releases/2003/05/20030531-2.html] (Last visited Sep. 8,


10See White House Press Release, Iran's Nuclear Program Concerns Bush Administration,
June 18, 2003, available at [http://usinfo.state.gov/topical/pol/arms/03061804.htm] (Last
visited Sept. 2, 2003) (indicating that negotiations are underway to design a plan for a
cooperative interdiction effort).

destruction, but also to eliminate or roll back such weapons from rogue states and11
terrorist groups that already possess them or are close to doing so.
Rather than seeking to change existing treaties or negotiate new ones, the PSI
appears to rely on international agreements that will enhance cooperation in
interdiction efforts, including sharing information and conducting exercises using
military or civilian assets to develop the participating nations’ ability to conduct air,12
ground, and maritime interception. However, recognizing that cooperation may not
always be forthcoming from all nations whose assistance is requested, the13
Administration has intimated that it will act unilaterally, if necessary.
These developments raise questions related to the international law of
jurisdiction. International law outlines the bounds of the permissible conduct for
purposes of self-defense and law enforcement activities abroad, insofar as some
activities could be viewed as unwarranted or unlawful interference with the rights of
other nations to conduct international commerce and maintain sovereignty over their
territory. This report provides an overview of the international law of the sea as it
relates to the permissible range of methods for interdicting WMD-related contraband
on the sea and in the air, and also of selected pertinent international regimes and
agreements. After a short outline of the current legal regime for the international
control of WMD, the report outlines the basic concepts of jurisdiction in international
law. Next, the report describes concepts central to the law of the sea, the rights and
limitations. The report then turns to the international legal framework limiting the
conduct of nations as it applies during times of war and peace, as well as during what
might be called “quasi war,” as is often deemed to be the case today.
Weapons of Mass Destruction –
International Legal Regime
From a U.S. perspective, the problem of controlling the proliferation of WMD
is particularly thorny because, unlike the control of illicit drugs, it does not suffice
to keep the materials from entering the United States or to prevent their manufacture
and dispersal on U.S. territory. Complete security from the dangers of a WMD attack

11Nonproliferation Policy after Iraq, Hearings before the House Committee on International
Relations, 108th Cong., June 4, 2003 (testimony of John R. Bolton), available online at 2003
WL 21299971 (Westlaw).
12See Australian Department of Foreign Affairs and Trade, Chairman’s Statement, Brisbane
Meeting of the Proliferation Security Initiative, available at
[http://www.dfat.gov.au/globalissues/psi/index.html] (Last visited Sept. 2, 2003).
Participants include Australia, France, Germany, Italy, Japan, the Netherlands, Poland,
Portugal, Spain, the United Kingdom and the United States. The PSI countries reached an
initial agreement at their third meeting, held in Paris September 3-4, 2003, and released a
“Statement of Interdiction Principles.”
13See NSS, supra note 2, at 6 (“While the United States will constantly strive to enlist the
support of the international community, we will not hesitate to act alone, if necessary, to
exercise our right of self-defense by acting preemptively against ... terrorists, to prevent
them from doing harm against our people and our country...”).

would require that dangerous materials be kept out of the hands of any potential
enemy. Moreover, some materials that can be used in the production of WMD also
have peaceful uses, and may even be necessary for the operation of wholly legitimate
industries. Interference in the trade of “dual use” materials could impair the ability
of other States to carry out legitimate trade, possibly leading to international discord.
Finally, under international law, sovereign States have the right in general to possess
weapons for their self-defense. Only the use of such weapons is constricted by
customary international law.14 While many States have agreed to limit their
production and possession of some types of WMD and conventional weapons, they
may have conditioned their consent on the conduct of other States, and may be able
to revoke their consent in accordance with any such conditional agreement. While
secret development of WMD on the part of a State that has agreed not to engage in
such conduct would constitute a breach of a treaty obligation, it is not necessarily a
crime or an act of aggression under international law merely to possess such
Nuclear Weapons
The center of the nuclear nonproliferation regime is the Nuclear
Nonproliferation Treaty (“NPT”).15 The treaty defines nuclear weapons States as
those States that had manufactured and detonated a nuclear weapon prior to January
1, 1967.16 The treaty thus allows five nuclear powers – the United States, Great
Britain, Russia, France and China – to manufacture and possess nuclear weapons, but
prohibits the transfer of such weapons to other States.17 All other States Parties to
the NPT have agreed not to acquire nuclear weapons in return for assistance in
developing peaceful uses for nuclear power.18 The five declared nuclear powers are
committed under the treaty to “pursue negotiations in good faith on effective
measures relating to cessation of the nuclear arms race at an early date and to nuclear
disarmament, and on a treaty on general and complete disarmament under strict and

14See, e.g., Legality of the Threat or Use of Nuclear Weapons, 1996 ICJ 226 (July 8),
reprinted in 35 ILM 809 (1996)(possession of nuclear weapons not per se unlawful; use of
nuclear weapons must conform to the U.N. Charter and the law of war) .
15Treaty on the Non-Proliferation of Nuclear Weapons, 21 UST 483 (1970) [hereinafter
“NPT”] .
16For a review of the nonproliferation framework, see generally Proliferation Control
Regimes: Background and Status, CRS Report RL31559.
17The NPT states that
Each nuclear-weapon State Party to the Treaty undertakes not to transfer to any recipient
whatsoever nuclear weapons or other nuclear explosive devices or control over such
weapons or explosive devices directly, or indirectly; and not in any way to assist,
encourage, or induce any non-nuclear-weapon State to manufacture or otherwise acquire
nuclear weapons or other nuclear explosive devices, or control over such weapons or
explosive devices.
NPT, supra note 15, art. I.
18As of December, 2002, the NPT had 188 members. Information about membership can
be found at [http://www.iaea.org/worldatom/Documents/Legal/npt_status.shtml].

effective international control.”19 States Parties may withdraw from the NPT on three
months’ notice if “extraordinary events, related to the subject matter of [the NPT],
have jeopardized the supreme interests of its country.”20
The chief means of verification is through inspections carried out by the
International Atomic Energy Agency (“IAEA”). Non-nuclear-weapon States Parties
may stockpile weapons-grade nuclear material, provided that the nuclear material is
subject to IAEA safeguards. Each non-nuclear State Party is required to negotiate a
set of safeguards for verification and accounting of nuclear materials at its declared
nuclear sites. No State Party is permitted to transfer nuclear materials or equipment
for processing them to any non-nuclear State for peaceful purposes unless the
transferred goods are subject to IAEA safeguards.21 The IAEA is empowered to
conduct “special inspections” if a State Party reports a loss of inspected material, but
is not empowered to take any action if it suspects that clandestine nuclear programs
are taking place at undisclosed sites. In the event it discovers a violation, the IAEA
is to report the noncompliance to the U.N. Security Council and General Assembly,
as with other arms control agreements. Neither the NPT nor IAEA regulations
provides for any penalty in case of breach.22
The restriction on the transfer of nuclear weapons and related technology is
implemented at the national level through export control laws.23 Some nations have
joined together to form multilateral export control groups in order to coordinate
nonproliferation efforts.24 These groups harmonize lists of sensitive materials and
technologies that must be controlled in order to prevent proliferation of nuclear
weapons and methods by which member countries are to prevent their transfer.
Regime members agree to restrict such trade by implementing laws, regulations, and
licensing requirements applicable to citizens and residents. They may also agree to
share information about exports and licenses. The regimes are voluntary and non-

19NPT, supra note 15, art. VI.
20Id. art. X. North Korea withdrew from the NPT in January, 2003. See North Korea's
Nuclear Weapons Program, CRS Issue Brief IB91141.
21NPT, supra note 15, art. III(2).
22See Barry Kellman, Bridling the International Trade of Catastrophic Weaponry, 43 AM.
U. L. REV. 755, 805 (1994).
23For an overview of U.S. proliferation sanctions, see Nuclear, Biological, Chemical, and
Missile Proliferation Sanctions: Selected Current Law, CRS Report RL31502.
24See U.S. General Accounting Office, Nonproliferation: Strategy Needed to Strengthen
Multilateral Export Control Regimes, GAO-03-43, October 2002 (assessing principal multi-
lateral export regimes).
25See id. at 1.

Chemical Weapons
International efforts to prohibit the use of chemical weapons began more than
a century ago as part of the effort to regulate warfare. The Hague Convention of
1907 explicitly forbade the use of poison or poisoned weapons.26 The 1925 Geneva
Protocol prohibited the use of asphyxiating, poisonous, or other gases, all analogous
liquids, materials or devices, and bacteriological methods of warfare.27 The first
convention to prohibit the manufacture and stockpiling of chemical weapons is the
Chemical Weapons Convention (“CWC”).28 The CWC calls for all State Parties to
eliminate their chemical weapons supplies by 2007 and restrict their trade in
“precursors” – chemicals that can be used in the production of weapons as well as for
peaceful uses – to other States Parties. States Parties agree to cease production and
stockpiling of weapons, declare all facilities that produce restricted chemicals for
non-prohibited uses, submit to verification inspections, and pass legislation
implementing the CWC, including criminalizing violations.29
The convention also creates the Organization for the Prohibition of Chemical
Weapons (“OPCW”) to monitor the implementation of the convention. The OPCW
carries out routine inspections of the relevant facilities on the territory of States
Parties to verify the accuracy of annual declarations regarding scheduled chemicals.
The OPCW may also carry out a “challenge” inspection in response to allegations of
noncompliance by one State Party with respect to another. The Conference of States
Parties addresses concerns over noncompliance, but other than requesting a breaching
member to comply or requesting action on the part of the U.N. Security Council, the

26See “Regulations Respecting the Laws and Customs of War on Land,” annexed to Hague
Convention No. IV art. 23(a), 36 Stat. 2277 (1907).
27Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous, or Other Gases,
and of Bacteriological Methods of Warfare, 26 U.S.T. 571 (1925)[“Geneva Protocol”]. The
United States ratified the Protocol in 1975.
28Convention on the Prohibition of the Development, Production, Stockpiling and Use of
Chemical Weapons and on Their Destruction, Jan. 13, 1993, 1974 U.N.T.S. 45 [hereinafter
“CWC”]. The United States ratified the CWC in 1997. There are currently 153 States
Parties. For a current status of members, visit [http://www.opcw.org/html/db/
me mb e r s _ f r a me s e t . h t ml ] .
29Id. art. VII(1) requires each member State to:
(a) Prohibit natural and legal persons anywhere on its territory or in any other place under
its jurisdiction as recognized by international law from undertaking any activity prohibited
to a State Party under this Convention, including enacting penal legislation with respect
to such activity;
(b) Not permit in any place under its control any activity prohibited to a State Party under
this Convention; and
(c) Extend its penal legislation enacted under subparagraph (a) to any activity prohibited
to a State Party under this Convention undertaken anywhere by natural persons,
possessing its nationality, in conformity with international law.
For details on U.S. implementing law for the CWC, see Chemical Weapons Convention:
Issues for Congress, CRS Issue Brief IB94029.

extent of remedial measures that might be imposed by the Conference is not
Biological Weapons
Biological weapons were first addressed in the Geneva Protocol of 1925,31
which banned only their use and not their manufacture, stockpiling, or transfer to
other States. The Biological Weapons Convention (“BWC”)32 addresses the
development, production, acquisition, or stockpiling of “[m]icrobial or other
biological agents, or toxins whatever their origin or method of production, of types
and in quantities that have no justification for prophylactic, protective or other
peaceful purposes” as well as “[w]eapons, equipment or means of delivery designed
to use such agents or toxins for hostile purposes or in armed conflict.”33 States Parties
to the BWC undertake to prohibit the above conduct, destroy biological weapons
supplies already on hand, and “not to transfer to any recipient whatsoever, directly
or indirectly, and not in any way to assist, encourage, or induce any State, group of
States or international organizations to manufacture or otherwise acquire any of the
agents, toxins, weapons, equipment or means of delivery specified in article I of [the
BW C ] . ” 34
The BWC does not contain provisions for verifying compliance of member
States. Efforts are underway to negotiate a protocol to strengthen the BWC by
creating a body to inspect compliance based on the model of the CWC.35 The Bush
Administration rejected the BWC Protocol while it was being drafted, objecting to
its “approaches to the issue.”36 A State Party that believes another State Party to be
in breach of its obligations may complain and present evidence to the U.N. Security
Council. The Security Council may initiate an investigation, with which the accused

30See Kellman, supra note 22, at 815.
31See Geneva Protocol, supra note 27 (States Parties agree to refrain from use of
“bacteriological” weapons).
32Convention on the Prohibition of the Development, Production, and Stockpiling of
Bacteriological (Biological) and Toxin Weapons and on Their Destruction, Apr. 10, 1972,
26 U.S.T. 583, 1015 U.N.T.S. 163 [hereinafter “BWC”]. As of October 2002, there were

146 States Parties. For membership status, visit [http://www.opbw.org/].

33BWC, supra note 32, art. I.
34Id. art. III.
35See (Draft “Rolling Text” of a) Protocol to the Convention on the Prohibition of the
Development, Production, and Stockpiling of Bacteriological (Biological) and Toxic
Weapons and on Their destruction, BWC Doc. BWC/AD HOC GROUP/55-1, Annex I, at
[http://www.opbw.org/ahg/docs/ rolling%20text%20and%20annexes.pdf] [hereinafter BWC
Protocol]; Jeremy Ostrander, Changing Direction on Non-nuclear Arms Control? American
Exceptionalism, Power, and Constancy, 21 BERKELEY J. INT'L L. 495, 501-02
(2003)(providing overview of BCW Protocol).
36See Statement by the United States to the Ad Hoc Group of Biological Weapons
Convention States Parties, Ambassador Donald Mahley, U.S. Special Negotiator for
Chemical and Biological Arms Control Issues, July 25, 2001, available at
[http://www.state.gov/t/ac/rls/rm/2001/5497pf.htm] (Last visited Sept. 3, 2003).

is bound to cooperate,37 but no further remedial measures are specified. States may
withdraw from the BWC on three months’ notice.38
Limitation on Enforcement
Although most observers conclude that arms control treaties have had important
restraining effects on the proliferation of weapons of mass destruction, it is apparent
that the conventions only apply to States that choose to join them and remain party
to them. Non-member States may have difficulty procuring WMD-related
technology and materials from States Parties to the respective treaties, but may trade
freely among themselves and are under no legal bounds to refrain from stockpiling
such weapons or transferring them to terrorist organizations and other entities, or
from conducting research to develop new ones. States Parties participate on a
voluntary basis, and may choose to back out of the conventions at any time, as was
the case when North Korea backed out of the NPT. The success of the arrangements
depends on the cooperation of member States and their ability and willingness to
enforce their own laws prohibiting acquisitions and exports of WMD-related
Jurisdiction under International Law
The concept of ‘sovereignty’ lies at the heart of the international political
system. Nation-states (States) are considered the “international persons” who are
both the creators and the subjects of international law. Each State is independent and
has supreme authority over its territory and general authority over its citizens. The
term “jurisdiction” refers to the authority of the State to affect the legal interests of
individuals and entities. Jurisdiction may describe a State’s authority to make its law
applicable to certain actors, events, or things (jurisdiction to prescribe); a State’s
authority to subject certain persons or things to the processes of its courts
(jurisdiction to adjudicate); or a State’s authority to compel compliance with its laws
and punish transgressors (jurisdiction to enforce).39 The ability to interdict, seize, and
destroy weapons would most significantly implicate the jurisdiction to prescribe and
enforce under international law.
A State’s ability legally to assert jurisdiction over persons and things within its
reach depends on principles of international law designed to prioritize the rights of
various States which may have a claim to jurisdiction over a matter. Historically, the
most commonly asserted basis for jurisdiction is the “territoriality principle”
(determining jurisdiction by reference to the place where the offense is committed).40
Other bases of jurisdiction include the “nationality principle” (determining

37BWC, supra note 32, art. VI.
38Id. art. XIII.
40See id. § 402, at comment c.

jurisdiction by reference to the nationality of the person accused of committing the
offense); the “protective principle” (determining jurisdiction by reference to the
national interest injured by the offense); and the “passive personality principle”
(determining jurisdiction by reference to the nationality of the victim). Where more
than one State can assert jurisdiction over a particular matter, the State with the
greatest interest should prevail.41
The right of each state to control its sovereign territory and the territorial waters
extending no more than 12 miles from its coast (“territorial sea”) is well-recognized
in international law. States may also exercise extraterritorial jurisdiction under
certain circumstances, but in general, this does not include the right to enforce laws
on the territory of another State without that State’s permission. For certain crimes,
there may exist “universal jurisdiction” permitting a State to try crimes that occurred
outside of its territory that did not involve any of its nationals, but the scope of
universal jurisdiction is not well-settled, and may not include the authority to take
enforcement action on the territory of another state without its permission. At any
rate, the possession or delivery of WMD or related materials is not generally
recognized as a crime subject to universal jurisdiction, like such international crimes
as piracy or slave trade.
Under international law, the United States clearly has authority to regulate the
possession or transfer of WMD materials within or across its borders and, subject to
any right to innocent passage,42 within its territorial waters and airspace. The United
States can also place restrictions on the conduct of U.S. citizens anywhere in the
world43 with regard to WMD under the principle of nationality;44 however, that
authority does not encompass a right to carry out law enforcement activities in
another State without its permission. Furthermore, if U.S. law enforcement or
military forces encounter WMD trade outside the territory of the United States, even

41See id. § 403. An evaluation of whether exercise of jurisdiction is reasonable, or to
determine which country has the greatest interest in pursuing a case, includes the territorial
link between the State and the regulated conduct or its effects; the connection between the
State and the person principally responsible for the regulated conduct or the persons the
regulation is designed to protect (such as nationality or residence); the relative importance
for the State to regulate the activity; the extent to which another State may have an interest
in regulating the activity; and the likelihood of conflict with regulation by another State,
among other considerations.
42Foreign flagged vessels have a right of unimpeded passage through the territorial sea of
a coastal state provided their voyage is “innocent.” UNCLOS, supra note 47, art. 17; see
generally Donald R Rothwell, Innocent Passage in the Territorial Sea: The UNCLOS
Regime and Asia Pacific State Practice in NAVIGATIONAL RIGHTS AND FREEDOMS AND THE
NEW LAW OF THE SEA 74 (2000). The coastal State may impose regulations for ships
carrying “inherently dangerous or noxious substances” or limit these ships to the special sea
lanes. UNCLOS, supra note 47, art. 22(2). See infra section entitled “Territorial Seas.”
43U.S. citizens abroad are also subject to the jurisdiction of the State on whose territory they
are present, and may also be liable for crimes against a State or its citizens even when the
crime is committed outside of the territory of that state. Citizens traveling abroad may find
themselves subject to conflicting obligations.
44See RESTATEMENT, supra note 39, § 402(2).

if the activity is unlawful under the laws of the State where it takes place or violates
the international obligations of any State, there is no automatic authority under
international law for U.S. forces to take action to thwart it.
Efforts to interdict WMD-related materials outside the territory of the United
States would fall within the boundaries of customary international law, including the
law of the sea, and any relevant multilateral or bilateral agreements the United States
has entered into. Specific instances determined by the United Nations Security
Council to constitute aggression or a threat to international peace and security may
be dealt with through action under Chapter VII of the U.N. Charter.45 Specific threats
to the United States that amount to an armed attack or imminent threat of an armed
attack may justify a belligerent response, such as the implementation of a blockade
or the use of armed force in self defense. Such a response could draw reactions from
other States and possibly escalate into a full-blown armed conflict.
Thus, the permissibility of options available to combat the proliferation of
WMD varies according to where the action takes place and whose laws are said to
be broken. While enforcement activity by a sovereign power over its own territory
has relatively few international implications, actions in the territory of another State
would implicate the sovereignty of that State, and would be subject to that State’s
terms of agreement or willingness and capacity to resist. Enforcement action in
places where no State has sovereign authority, such as the high seas, may meet with
relatively light resistance from other States, but remains subject to international law.
The Law of the Sea
The law of the sea divides authority among nations to conduct activity in or
above the oceans and external waterways that both divide and connect nations. The
basic rules of international law with respect to jurisdiction over vessels on the high
seas are set forth in the Convention on the High Seas46 and the more recent United47
Nations Law of the Sea Convention (UNCLOS). The United States is a Party to the
first convention and is a signatory, but not a Party, to UNCLOS.48 However, even
while objecting to certain parts of the latter convention when it was first concluded
in 1982, the United States has acknowledged that its provisions concerning

45For example, in 1990 the U.N. Security Council authorized member states to enforce
sanctions against Iraq. Coalition naval forces intercepted more than 15,000 vessels pursuant
to Security Council resolutions 661, 665, and 670. See Lois E. Fielding, Maritime
Interception Centerpiece of Economic Sanctions in the New World Order, 53 LA. L. REV.
1191, 1192-94 (1993)(suggesting the “Persian Gulf interception” could serve as a paradigm
for maritime interdiction to maintain peace and stability of the world order).
46Convention on the High Seas, April 29, 1958, 13 U.S.T. 2312, 450 U.N.T.S. 82.
47United Nations Convention on the Law of the Sea, opened for signature Dec. 10, 1982,
U.N. Doc A/CONF.62/122 (1982) (entered into force Nov. 16, 1994)[hereinafter
“UNCLOS”]; S. TREATY DOC. 103-39 (Oct. 7, 1994).
48For a discussion of issues surrounding possible U.S. ratification, see The Law of the Sea
Convention and U.S. Policy, CRS Issue Brief IB95010.

navigation and the uses of the oceans “generally confirm existing maritime law and
practice and fairly balance the interests of all states.”49 Both conventions affirm that
the high seas are open to all States, that freedom of navigation is a basic freedom of
the high seas, and that every State has “the right to sail ships under its flag on the
high seas.”50 The law of the sea balances the rights of maritime States to navigate
freely with the rights of coastal States to maintain security. It also deals with some
aspects of air transportation, applying to aircraft some, but not all, of the rules that
apply to maritime vessels.
Legal Divisions of Waters
Under the law of the sea, the world’s waters are divided into two basic
categories: national and international waters.51 The legal status of the waters
determines the rights and obligations of States and their vessels, public and private.
National waters include internal waters (lakes and rivers, some harbors and bays, and
other waters that lie between the actual shoreline and the claimed baseline52) of a
coastal State and its territorial sea. The State has complete sovereign control over
internal waters, and consent must be given for any vessel to enter or for aircraft to fly
over it except in cases of emergency.53 Any private vessel that enters the internal
waters of a coastal State is subject to the jurisdiction of that State and may be stopped
and searched by military or law enforcement personnel in accordance with the
domestic law of the State.
Territorial Seas. A coastal State may claim sovereignty over the waters
extending “up to a limit not exceeding 12 nautical miles” beyond the baseline as its54
territorial sea. A State may exercise sovereignty over its territorial sea, but its rights
are subject to foreign vessels’ right of innocent passage. UNCLOS provides that
foreign flagged vessels have the right of unimpeded passage through the territorial
sea of a coastal State provided passage is “innocent,” meaning the ship’s conduct is
“not prejudicial to the peace, good order or security of the coastal State” and takes

49“Statement on United States Oceans Policy of March 10, 1983,” PUBLIC PAPERS OF THE
renegotiation of the part of UNCLOS concerning deep seabed mining, President Clinton
submitted the convention to the Senate for its advice and consent in 1994; it remains
pending in the Senate Foreign Relations Committee. S. TREATY DOC. 103-39 (Oct. 7, 1994).
50Convention on the High Seas, supra note 46, arts. 2 and 4; UNCLOS, supra note 47, arts.

87 and 90.

OPERATIONS 14 (A.R. Thomas and James C. Duncan, eds., 1999)[hereinafter CDR’S
52Baselines are ordinarily set at the low-water mark of a coast as annotated on large-scale
charts issued by the coastal State. See John Astley and Michael Schmitt, The Law of the Sea
and Naval Operations, 42 A.F. L. Rev. 119, 122 (1997) (explaining how maritime baselines
are drawn and why they are frequently subjects of dispute).
53See CDR’S HANDBOOK, supra note 51, at 215 (ports may not be closed to genuinely
distressed vessels).
54UNCLOS, supra note 47, art. 3.

place in conformity with international law.55 The right of innocent passage does not
apply to aircraft. Conduct that is considered prejudicial includes military exercises,
launching of aircraft or weapons, intelligence collection, research, fishing, or
dumping pollutants.56 Submarines must remain on the surface during their voyage
through territorial seas.57 Vessels may drop anchor or participate in a rescue mission
only in case of distress.58 It is worth noting that cargo, destination, or ultimate
purpose are not among the criteria to be used to determine whether passage is
The coastal State is permitted to implement certain regulations in its territorial
sea if necessary to protect resources, for example, so long as the restrictions are
necessary and reasonable, are implemented in a non-discriminatory fashion, and do
not have the practical effect of denying or impairing the right of innocent passage.
While the conventions do not require notification or permission of the coastal State
in order for foreign flagged vessels to transit through a territorial sea, some States
have nonetheless prescribed special measures with respect to warships.60 The United
States takes the position that such measures do not comport with the law of the sea,
and frequently carries out Freedom of Navigation (FON) exercises to demonstrate its
non-acquiescence to the claimed rights.61
Contiguous Zones and Exclusive Economic Zones (EEZ). The
Conventions also recognize that every coastal State may lay more limited claim to
a number of maritime zones in the international waters extending beyond the
territorial sea. A State may establish a zone adjacent to its territorial sea as a
“contiguous zone.” Within this zone the coastal State is not sovereign, but it may
exercise the control necessary to prevent and punish infringements of the customs,
fiscal, immigration, and sanitary laws and regulations that apply in its territorial sea.
The contiguous zone may extend up to 24 miles from the coast. Up to 200 miles from
the coast may be claimed as an Exclusive Economic Zone (EEZ), in which the
coastal State may exploit the natural resources. For the purpose of exercising
jurisdiction to enforce the law, the areas beyond the territorial sea of any coastal State
are treated as the high seas.

55Id. arts. 17-19.
56Id. art. 19.
57Id. art. 20.
58United Nations Convention on the Territorial Sea and the Contiguous Zone 29 April 1958,
art. 14(3), 15 UST 1606; Convention on the High Seas, supra note 46, art. 12,; UNCLOS,
supra note 47 art. 18.
Chapter 7, at 6 (2003). Some countries have taken the position that nuclear powered
warships and vessels carrying nuclear materials may be subject to special requirements. See
A.V. Lowe, The Commander’s Handbook on the Law of Naval Operations and the
Contemporary Law of the Sea, in THE LAW OF NAVAL OPERATIONS 109, 115-16 (Robertson
ed. 1991)(noting that regulations that amount to a denial of passage are likely unlawful).
60See Astley and Schmitt, supra note 52, at 132.

Straits. Straits overlapped by the territorial seas of coastal nations that are
used for international navigation from one part of the high seas or an exclusive
economic zone to another similar area are subject to a special regime different from
that of ordinary territorial seas, known as transit passage.62 The vessels and aircraft
of all nations have the right to unimpeded transit through the straits in their ordinary
mode of travel (submarines may remain submerged). Ships and aircraft navigating
through straits must proceed without delay, must refrain from using or threatening
to use force, and may not engage in any activities other than those incident to their63
normal and expeditious travel. Coastal nations may not suspend or hamper the right
of transit when they are not at war, even with respect to warships of belligerent64
nations at war with others. However, coastal States may impose requirements for
safe navigation, such as requiring ships to use delineated shipping lanes.6566
Archipelagic waters are treated similarly.
The High Seas. According to the 1958 Convention on the High Seas, the
term “high seas” means “all parts of the sea that are not included in the territorial sea
or in the internal waters of a state.”67 Incorporating customary international law, the
1958 Convention further states that “no State may validly purport to subject any part
of them to its sovereignty.” The ships of all nations, whether coastal or land-locked,
enjoy the freedom to navigate, fish, and lay pipelines or cables.68 UNCLOS adds two
new freedoms: to conduct scientific research and to build artificial islands and other
installations (subject to Part IV of UNCLOS).69 These freedoms are to be exercised
with “due regard for the interests of other States in their exercise of the freedom of
the high seas, and also with due regard for the rights under this Convention with
respect to activities in the Area.”70
Legal Status of Vessels
For determining jurisdiction over ships on the high seas, it is necessary to know
the nationality of the vessel and whether it is operated by a government or by some
private entity. Ordinarily, on the high seas, a ship is under the “exclusive71
jurisdiction” of the State whose flag it flies. Warships and State-owned or operated
vessels “used only on government non-commercial service” are said to enjoy

62UNCLOS, supra note 47, arts. 37 et seq. The Convention on the High Seas did not include
a right of transit passage.
63UNCLOS, supra note 47, art. 39(1). Ships may drop anchor or carry out other necessary
activities in case of distress or force majeure.
64UNCLOS, supra note 47, art. 44; see CDR’S HANDBOOK, supra note 51, at 125.
65UNCLOS, supra note 47, art. 41.
66See id. art. 53.
67Convention on the High Seas, supra note 46, art. 1.
68Id. art 2.
69UNCLOS, supra note 47, art. 87.
71Convention on the High Seas, supra note 46, art. 11; UNCLOS, supra note 47, art. 94.

“complete immunity” from the jurisdiction of non-flag States.72 Merchant ships, on
the other hand, are subject to a number of exceptions to exclusive flag State
Nationality. The Convention on the High Seas and UNCLOS both mandate
that ships may sail “under the flag of one State only” and that “[a] ship may not
change its flag during a voyage or while in a port of call, save in the case of a real
transfer of ownership or change of its registry.”73 Both further mandate that every
State “shall fix the conditions for the grant of its nationality to ships, for the
registration of ships in its territory, and for the right to fly its flag.”74 States may
maintain “open registries” of vessels, meaning a foreign national may register a
vessel and have the right to fly that States flag as a “flag of convenience,” enjoying75
the protection of that State. A ship that flies the flags of two or more States, or that
flies no flag at all, is considered stateless.
Status of Warships. Warships are defined as ships belonging to the armed
forces of a State and bearing its flag, commanded by a commissioned officer of that
State and operated by a crew that is under the discipline of that State’s armed
forces.76 Warships enjoy sovereign immunity and are not subject to arrest and search
by the warships of other States on the high seas or in territorial seas. Police and port
authorities may only board a warship with the permission of the Commanding
Officer. Warships are exempt from foreign regulations but are bound to comply with
established principles of international law. A warship is in effect the sovereign
territory of the country to which it belongs whether it is at sea or pierside in a foreign
port. A warship whose conduct does not conform with international principles may
be asked by the coastal State to leave its territorial waters, and is bound to comply
with such a request.77
Airspace and Aircraft
Prior to the advent of the airplane, the concept of sovereignty primarily
concerned rights over land and sea. As aerospace technologies developed at the start
of the twentieth century, making it possible for nations to exert some actual control
over activities in the skies above them, the concept of exclusive sovereignty over

72Convention on the High Seas, supra note 46, arts. 8 and 9; UNCLOS, supra note 47, arts.

95 and 96.

73Convention on the High Seas, supra note 46, art. 6; UNCLOS, supra note 47, art. 92.
74Convention on the High Seas, supra note 46, art. 5; UNCLOS, supra note 47, art. 91.
75There must be a genuine link between the vessel and the flag State. Convention on the
High Seas, supra note 46, art. 5. The United States the position that only the flag State may
challenge the validity of a registration. See Restatement, supra note 39, § 501 (citing
Lauritzen v. Larsen, 345 U.S. 571 (1953)).
76Convention on the High Seas, supra note 46, art. 82; UNCLOS, supra note 47, art. 29.
77UNCLOS, supra note 47, art. 30; Convention on the Territorial Sea and the Contiguous
Zone, supra note 58, art. 23.

airspace super-adjacent to the territory of a State quickly coalesced into customary
international law.78 While freedom of navigation for commercial purposes was
supported in theory, States also saw the military threat made possible by air power
as a concern.79 As a result, some parts of the customary law of the sea have adapted
to apply to aircraft, but other law has been developed through treaty.80
Law of the Sea Conventions. Where airspace is treated in the conventions
on the law of the sea, it is generally divided into national and international airspace,
with national airspace including that above the territorial sea. There is no right of
innocent passage for overflight of the territorial sea of a coastal State, but the rules
of transit passage over straits and archipelagic waters apply to aircraft as well as
ships, even though the airspace is considered national. The Convention on the High81
Seas includes the airspace above international waters in the freedom to navigate.
It is unclear whether rights and privileges accorded to “ships” extend by analogy to
aircraft where the conventions do not specifically address them, such as the right to
land an aircraft without permission in situations of distress.82
Chicago Convention. The 1944 Convention on International Civil Aviation
(Chicago Aviation) explicitly recognizes that “every State has complete and
exclusive sovereignty over the airspace above its territory.”83 “Territory” includes
the territorial seas.84 Presumably, all non-territorial airspace is international.
The Chicago Convention applies on its face only to civil aircraft, but specifies
which aircraft are considered state aircraft (those used in military, customs, or police
services) and places some duties and restrictions on them. Article 3 states that “[n]o
state aircraft ... shall fly over the territory of another State or land thereon without
authorization...” Contracting States commit to “hav[ing] due regard for the safety of
navigation of civil aircraft” when issuing regulations for their state aircraft.

78See Major Stephen M. Shrewsbury, September 11th and the Single European Sky:
Developing Concepts of Airspace Sovereignty, 68 J. AIR L. & COM. 115, 130 (2003)
(arguing that article 1 of the Convention Relating to the Regulation of Aerial Navigation,
Oct. 13, 1919, 11 L.N.T.S. 173, effectively codified customary law developed over the
previous twenty years).
79See id.
7-8 (1987)(noting that the “freedom of the seas” model was rejected for the airways in favor
of “air sovereignty,” insuring that national governments would play a dominant role in
aviation development).
81Convention on the High Seas, supra note 46, art. 2; UNCLOS, supra note 47, art. 2(2).
82The texts of the conventions are silent on this point, however, States have asserted the right
to land aircraft on foreign soil in case of emergency. See, e.g., Collision of U.S. and
Chinese Aircraft: Selected Legal Considerations, CRS Report for Congress RS20876.
83Convention on International Civil Aviation, Dec. 7, 1944, art. 1, 61 Stat. 1180, T.I.A.S.
No. 1591 [hereinafter “Chicago Convention”].
84Id. art. 2.

Contracting States also agree “not to use civil aviation for any purpose inconsistent
with the aims of [the] Convention.”85
While the Chicago Convention did not adopt the liberal freedom of navigation
regime for aircraft supported by the United States,86 the Convention does permit the
civil aircraft of contracting States that are not engaged in scheduled flights to “make
flights into” each others’ territories and to make stops for non-traffic purposes
without the necessity of obtaining prior permission ...” subject to a possible
requirement for landing.87 States may regulate air traffic above their territories
without distinction based on nationality (with respect to other contracting States).88
However, States may designate areas off-limits for reasons of military necessity or
public safety, provided no distinction is made between nationality of the aircraft.89
Scheduled flight services may be operated over or into the territory of a contracting
State only with that State’s permission and in accordance with the terms it may set.90
Overflights using pilotless aircraft require special authorization.91
Nationality of Aircraft. Like ships on the seas, aircraft must be registered in
one State only,92 and must bear the appropriate markings indicating nationality and93
registrations. Civil aircraft are subject to regulation both by the State of registration
and, while flying over the territory of another State, that State’s applicable
regulations. Civil aircraft are also required to carry certain documents, including a
certification of airworthiness, log book, radio license, a passenger list and a manifest94
of cargo. No munitions or implements of war may be carried as cargo over a State’s
territory without its permission.95 States may make other restrictions with regard to
cargo for reasons of public order and safety, provided the rules do not discriminate
based on nationality.

85Id. art. 4. These aims include the avoidance of international friction and the promotion of
international cooperation, in furtherance of maintaining peace. See id. preamble. However,
it does not prevent States from acting in self-defense in accordance with the United Nations
Charter. See id. art. 89 (“In case of war, the provisions of this Convention shall not affect
the freedom of action of any of the contracting States affected, whether as belligerents or
as neutrals. The same principle shall apply in the case of any contracting State which
declares a state of national emergency and notifies the fact to the Council.”).
Dempsey, supra note 80, at 11 (describing the “five freedoms” called for by American
87Chicago Convention, supra note 83, art. 5.
88Id. arts. 11-12.
89Id. art. 9.
90Id. art. 6.
91Id. art. 8.
92Id. arts. 18-19.
93Id. art. 20.
94Id. art. 29.
95Id. art. 35.

State Aircraft. Under the Chicago Convention, the status of state aircraft is
determined according to use rather than strictly by state ownership.96 The Chicago
Convention does not, however, enumerate rules governing state aircraft. Military
aircraft, probably comprising the largest category of state aircraft, are treated much
like warships. Military aircraft are defined under international law as those aircraft
“operated by commissioned units of the armed forces of a nation bearing the military
markings of that nation, commanded by a member of the armed forces, and manned
by a crew subject to regular armed forces discipline,”97 and are exempt from other
States’ law enforcement measures that apply to civil aircraft flying over their
territory.98 The crew of military aircraft are immune from the jurisdiction of the
territorial sovereign for acts performed during official duties. Foreign officials may
not board a state or military aircraft without the consent of its commander, and in the
event of a dispute regarding customs, immigration, or quarantine, the host nation is
limited to requesting that the state aircraft leave the national territory.99
Enforcement Options
The following sections address the rights and obligations of States and non-
public vessels and aircraft, which vary depending not only on location and status but
according to whether the situation is considered one of war or peace, or somewhere
in between. During peacetime, States generally employ law enforcement techniques,
for example, to restrict trade or interdict unlawful materials. International law also
permits States to enforce certain international prohibitions on or above the high seas.
Law Enforcement in National Waters and Airspace
The ability of a coastal State to assert jurisdiction over vessels of non-flag States
that do not enjoy sovereign immunity depends on which maritime zone the vessel is
located in and what it is doing. Maritime law enforcement measures may be taken
when there are reasonable grounds for believing that a vessel is violating the validly
applicable laws of the coastal State.100 A coastal State may interdict ships suspected
of engaging in illicit drug traffic, for example, without obtaining the permission of
the flag State, if the suspect vessel is located in the State’s internal waters,101
archipelagic waters, territorial sea, or, in some circumstances, its contiguous zone.
Warships of the coastal State are permitted to conduct hot pursuit of a foreign ship

96Id. art. 4. See also Michel Bourbonniere and Louis Haeck, Military Aircraft and
International Law: Chicago Opus 3, 66 J. AIR L. & COM. 885, 887-88 (2001)(discussing
determination of aircraft status).
97See CDR’s Handbook, supra note 51, § 2.2.1. Civilian owned and operated aircraft
contracted for use of the armed forces may be designated as “state aircraft,” in which case
they would also qualify for sovereign immunity. See id. § 2.2.3.
98See Bourbonniere and Haeck, supra note 96, at 891.
99See CDR’s Handbook, supra note 51, at 114.
100Id. at 235.
101See id.

beyond the limits of its territorial sea or contiguous zone if there is reason to believe
the ship violated the applicable laws and regulations of that State and the pursuit is
not interrupted.102 The coastal State may not discriminate against ships based on their
nationality or based on their cargoes to, from, or on behalf of any State.103 The
coastal State should not exercise criminal jurisdiction on board a foreign ship passing
innocently through its territorial sea for crimes committed on board the ship unless
the consequences of the crime extend to the coastal State, the crime disturbs the
“peace or good order,” the flag State or the captain of the vessel requests assistance,
or such measures are necessary to suppress the illicit traffic of drugs.104
Law Enforcement on the High Seas
Ordinarily, warships and other vessels used by States to enforce their laws on
the high seas may take action only against ships of the enforcing State’s nationality
or ships with ambiguous nationality. However, UNCLOS and the Convention on the
High Seas both identify certain activities as unlawful and allow States to take
enforcement measures to suppress them.
Unlawful Acts on the High Seas. Both conventions mandate all States to
take or adopt “effective measures to prevent and punish the transport of slaves in
ships authorized to fly its flag and to prevent the unlawful use of its flags for that105
purpose” and to “co-operate to the fullest possible extent in the repression of piracy
on the high seas.”106 Piracy is defined as illegal acts of violence, detention, or
depredation (plundering, robbing, or pillaging) for private ends in or over
international waters.107 Mutiny and hijacking do not amount to piracy unless the ship108
or aircraft seized is thereafter used to commit piratical acts. Acts that would
constitute piracy if committed for private ends are not piratical if committed for109
political ends, for example, by insurgents not recognized as belligerents.
UNCLOS further mandates that all States “co-operate in the suppression of
illicit traffic in narcotic drugs and psychotropic substances engaged in by ships on the
high seas contrary to international conventions” and “co-operate in the suppression
of unauthorized broadcasting from the high seas.”110 Neither convention addresses
the transport of weapons of mass destruction or of materials useful in the production
of such weapons.

102See id. at 432.
103Convention on the Territorial Sea and the Contiguous Zone, supra note 58, art. 15.
104Id. art. 19.
105Convention on the High Seas, Art. 13; UNCLOS, supra note 47, art. 99.
106Convention on the High Seas, Art. 14; UNCLOS, supra note 47, art. 100.
107CDR’S HANDBOOK, supra note 51, at 222.
108Id. at 224.
110UNCLOS, supra note 47, arts. 108-09.

Right of Approach and Visit. Merchant vessels, whether privately owned
or State owned, may be stopped and boarded by the warships of non-flag States under
certain circumstances. The Convention on the High Seas specifies that a warship
may stop and board a foreign merchant vessel if “there is reasonable ground for
suspecting (a) [t]hat the ship is engaged in piracy; or (b) [t]hat the ship is engaged in
the slave trade; or (c) [t]hat, though flying a foreign flag or refusing to show its flag,111
the ship is, in reality, of the same nationality as the warship.” UNCLOS reiterates
those justifications and adds two more – (1) “the ship is engaged in unauthorized112
broadcasting ...,” and (2) “the ship is without nationality.” With respect to the
latter justification, UNCLOS replicates language in the Convention on the High Seas
providing that “[a] ship which sails under the flags of two or more States, using them
according to convenience, may not claim any of the nationalities in question with113
respect to any other State, and may be assimilated to a ship without nationality.”
Both conventions provide that in the specified circumstances a warship “may
send a boat under the command of an officer to the suspected ship,” “proceed to
verify the ship’s right to fly its flag,” and “if suspicion remains after the documents
have been checked, ... proceed to a further examination on board the ship, which114
must be carried out with all possible consideration.”
Enforcement Measures. With the exception of piracy and international
broadcasting, however, neither convention specifies what actions a warship may take
if the initial or further examination confirms the suspicions that justified the boarding
in the first place. With respect to piracy, both conventions state that
[o]n the high seas, or in any other place outside the jurisdiction of any State,
every State may seize a pirate ship or aircraft, or a ship or aircraft taken by piracy
and under the control of pirates, and arrest the persons and seize the property on115
In the event the suspected pirate ship fleeing the pursuit of a warship enters a foreign
territorial sea, the pursuing warship should attempt to obtain the permission of the
State with sovereignty over the area prior to entering. If circumstances do not allow
such communication, the warship may be able to enter the territorial waters of
another state if necessary, but must depart immediately upon the request of the116
coastal State. A similar rule applies to piratical aircraft that flee into the national
airspace of another State.

111Convention on the High Seas, supra note 46, art. 21.
112UNCLOS, supra note 47, art. 110.
113Convention on the High Seas, supra note 46, Art. 6; UNCLOS, supra note 47, art. 92.
114Convention on the High Seas, supra note 46, art. 22; UNCLOS, supra note 47, art. 110.
115Convention on the High Seas, supra note 46, art. 19; UNCLOS, supra note 47, art. 105.
116CDR’S HANDBOOK, supra note 51, at 226.

With respect to a ship engaged in unauthorized international broadcasting,
UNCLOS provides that a State having jurisdiction117 “may ... arrest any person or
ship engaged in unauthorized broadcasting and seize the broadcasting apparatus.”118
Otherwise, both conventions simply state that “if the suspicions prove to be
unfounded, and provided that the ship boarded has not committed any act justifying
them, it shall be compensated for any loss or damage that may have been
Although neither convention explicitly says so, it also appears that any warship
may seize a merchant vessel that has no nationality. In United States v. Cortes,120 for
instance, the United States Court of Appeals for the Fifth Circuit held that the
Convention on the High Seas conferred no rights whatsoever on stateless vessels and
upheld the seizure of an unregistered ship found by the Coast Guard to be
transporting marijuana. It stated:
To secure the protection afforded foreign merchant vessels on the high seas, a
vessel must accept the duties imposed by registration. This the PITER failed to121
do; her crew cannot complain of the results.
Thus, with the exception of piracy, international broadcasting, and stateless
vessels, both the Convention on the High Seas and UNCLOS are silent with regard
to whether the consent of the flag State or further international agreement is
necessary for a State to seize a ship flying the flag of another State, confiscate its
cargo, or arrest and prosecute its officers and crew for engaging in other prohibited
activities.122 Absent consent or agreement, the exercise of jurisdiction over the

117The following states have jurisdiction over cases of unauthorized broadcasting:
(a) the flag State of the ship;
(b) the State of registry of the installation;
(c) the State of which the person is a national;
(d) any State where the transmissions can be received; or
(e) any State where authorized radio communication is suffering interference.
UNCLOS, supra note 47, art. 109.
119Convention on the High Seas, Art. 22; UNCLOS, supra note 47, art. 110.
120588 F.2d 106 (5th Cir. 1979).
121Id. at 110.
122RESTATEMENT, supra note 39, § 522 reporter’s note 3 notes that “[a] number of 19th
century treaties authorized naval and law enforcement vessels of a state to visit, inspect, and
seize vessels of another state engaged in slave trade and to bring the traders for trial before
special mixed courts of justice,” but that “[m]ost of these treaties are no longer in force.”
The existing slavery conventions to which the United States is a Party do not confer such
authority. See Convention to Suppress the Slave Trade and Slavery, 46 Stat. 2183 (1929)
and Supplementary Convention on the Abolition of Slavery, the Slave Trade and Institutions
and Practices Similar to Slavery, 18 UST 3201 (1967).
The United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic
Substances, TIAS ___ (1990) does not itself authorize Member States to seize the flagged

allegedly unlawful activities of a merchant vessel appears to remain the prerogative
and responsibility of the flag State. Weapons of mass destruction are not mentioned
in UNCLOS or the Convention on the High Seas. It therefore appears that the visit,
search, and possible seizure of ships on the high seas that might be engaged in
transporting weapons of mass destruction or materials useful in the production of
such weapons would not be authorized under the law of the sea as it currently stands.
The subject also does not appear to be directly addressed by the agreements and
informal arrangements that address the proliferation of weapons of mass
destruction,123 nor by the existing multilateral conventions on terrorism.124 Such an
authorization might well be negotiated on a bilateral or multilateral basis, could be
obtained on an ad hoc or more permanent basis, and, conceivably, could be given by
action of the Security Council.125 Otherwise, the interdiction of vessels and aircraft
on or over the high seas that are suspected of carrying WMD may only be valid as a
legitimate act of self defense or under a theory of “self-help,” as described below.
The Proliferation Security Initiative
The exact contours of the PSI have not yet been finalized, but the eleven PSI
States have held three meetings so far and have reportedly reached an agreement in
principle, releasing a “statement of interdiction principles” (see Appendix)
committing member States to take action “consistent with national legal authorities

vessels of other States suspected of engaging in the illicit traffic of narcotics but authorizes
(1) the flag State to request the assistance of other States on an ad hoc basis, (2) a State with
reasonable grounds to suspect that a vessel is engaged in such illicit commerce to inform the
flag State and to seek permission to take “appropriate measures” on an ad hoc basis, and (3)
the negotiation of agreements among the Parties permitting each Party to board, search, and
take other “appropriate action” regarding the merchant vessels of the other Parties to the
agreements suspected of engaging in narcotics trafficking. See id. art. 17. The United States
has since 1974 reportedly conducted a maritime narcotics interdiction program on the high
seas which routinely obtains flag state consent to the search and possible seizure of suspect
vessels on a case-by-case basis. See DEPARTMENT OF STATE, CUMULATIVE DIGEST OF
UNITED STATES PRACTICE IN INTERNATIONAL LAW 1981-1988, Book II (1994), at 1386-99.
The U.S. has also entered into bilateral treaties concerning narcotics trafficking that grant
standing authority for such searches and seizures. See, e.g., Agreement To Facilitate the
Interdiction by the United States of Vessels of the United Kingdom Suspected of Trafficking
in Drugs, 33 UST 4224 (1981) and Agreement for the Interdiction of Narcotics Trafficking,
TIAS 11123 (1985) (concluded with the Bahamas).
123See, e.g., NPT, supra note 15; BWC, supra note 32; CWC, supra note 28; see also Missile
Technology Control Regime (MTCR) and International Code of Conduct Against Ballistic
Missile Proliferation (ICOC): Background and Issues for Congress, CRS Report RL31848.
For a discussion of these and other non-proliferation efforts, see Proliferation Control
Regimes: Background and Status, CRS Report RL31559.
124See, e.g., the Convention for the Suppression of Unlawful Acts Against the Safety of
Maritime Navigation, TIAS ___ (1995) and the Vienna Convention on the Physical
Protection of Nuclear Material, TIAS 11080 (1987).
125For example, the U.N. Security Council authorized the enforcement of sanctions against
Iraq in response to the Iraqi invasion of Kuwait. See Fielding, supra note 45, at 1200 - 01
(describing Security Council Resolutions authorizing enforcement of sanctions against Iraq).

and relevant international law and frameworks, including the U.N. Security
Council.”126 According to the PSI nations’ statement, the initiative will target
“States or non-state actors of proliferation concern,” which are defined as
those countries or entities that the PSI participants involved establish should be
subject to interdiction activities because they are engaged in proliferation
through: (1) efforts to develop or acquire chemical, biological, or nuclear
weapons and associated delivery systems; or (2) transfers (either selling,127
receiving, or facilitating) of WMD, their delivery systems, or related materials.
The Bush Administration emphasized that the initiative is an effort to coordinate
export control regimes that are already in place, rather than a major departure from
the current nonproliferation regimes. This statement may represent a reconsideration
of the initial goal of the PSI; in announcing the initiative, President Bush explained
that the PSI would give member countries the capability to “search planes and ships
carrying suspect cargo and to seize illegal weapons or missile technologies.”128
To the extent that the searches and seizures are carried out on the high seas, the
law of the sea would clearly allow a PSI nation warship to stop and search vessels
flying its flag or no flag at all, or flying the flag of a State that consents to searches
of its ships for that purpose. Presumably, the PSI member States will allow ships
flying their flags to be searched for WMD materials prohibited by their laws where
reasonable suspicion exists, and non-member States could be asked to consent on an
ad hoc basis. However, it appears unlikely that States of proliferation concern, such
as the Democratic Republic of Korea or Iran, would consent to having their ships
boarded and searched for WMD materials, and even if consent were obtained, there
is no clear legal authority under international law, as it currently stands, for a State
to seize WMD materials it finds on board, even if the flag State is a member of the
relevant nonproliferation treaty.
PSI States carrying out interdiction activities at their port facilities have broad
authority to inspect vessels and prescribe law restricting the kinds of cargo vessels
are permitted to carry into port. However, for a PSI State to stop and search a vessel
traveling through its territorial sea could impede the vessel’s right of innocent
passage. According to the PSI statement of principles, participating States are
encouraged to “stop and/or search in their internal waters, territorial seas, or
contiguous zones (when declared) vessels that are reasonably suspected of carrying
[WMD-related] cargoes to or from states or non-state actors of proliferation concern
and to seize such cargoes that are identified,”and to “enforce conditions on vessels
entering or leaving their ports, internal waters or territorial seas that are reasonably
suspected of carrying such cargoes, such as requiring that such vessels be subject to
boarding, search, and seizure of such cargoes prior to entry.” These activities,

126White House Fact Sheet, Proliferation Security Initiative: Statement of Interdiction
Principles, Sep. 4, 2003, available at [http://www.whitehouse.gov/
news/releases/2003/09/20030904-11.html] (See infra Appendix A).
128See Bush, supra note 9.

however, are to be conducted only “to the extent their national legal authorities
permit and consistent with their obligations under international law and frameworks.”
Under traditional international law, the right of coastal States to prescribe law
applicable in their territorial seas and contiguous zones are restricted by the vessels’
flag State’s right of free navigation. The PSI States’ ability to intercept and search
vessels in those zones may require the consent of the flag-State, unless the vessels’
passage is non-innocent. It is open to debate whether coastal nations have the
jurisdiction to prohibit the carrying of all WMD-related materials through their
contiguous zones.129 Non-participating States may object to a requirement that their
vessels submit to inspection prior to entering the territorial seas of a coastal State as
an effective suspension of the right of innocent passage.
The interdiction of aircraft suspected of carrying WMD-related materials that
occurs in national airspace raises fewer legal issues, since there is no right of
innocent passage through airspace. However, international law calls for “due regard”
to the safety of civil aircraft. Measures involving the use of force to deny aircraft
passage or to enforce landings for inspections could raise objections from other
nations. 130
Belligerent Rights
During an armed conflict, of course, the rules of international law are
transformed. The law of neutrality delineates the rights and responsibilities of
belligerent and neutral States. In general, a neutral State maintains the basic rights
of inviolable territory and the practice of commerce (unless it involves providing
contraband to the belligerents), but the neutral State must abstain from participating
in the conflict and maintain its impartiality as to the belligerents. Failure of a neutral
ship to act accordingly may result in a determination by a belligerent that the neutral
has acquired enemy character. Likewise, a belligerent must respect a neutral’s
inviolability and its entitlement to trade, but has the right to insist on the neutral’s
impartiality and non-involvement in the conflict.
Belligerents are prohibited from conducting hostilities, establishing a base of
operations, or seeking sanctuary in neutral territory. The neutral State is responsible
for ensuring that its territory is not being used by the belligerents in a manner
inconsistent with its neutral status. In the event a neutral is unable or unwilling to
police its territory for that purpose, a belligerent may take action to put an end to the
misuse, even if such action requires the belligerent to enter the ordinarily inviolable
territorial sea of the neutral State. A neutral may prescribe conditions for belligerent
warships transiting its territorial seas – or even prohibit their passage altogether –
notwithstanding the customary right of innocent passage, as long as the regulations

129See Lowe, supra note 59, at 115-18.
130See Eric Edward Geiser, The Fog of Peace: The Use of Weapons Against Aircraft in
Flight During Peacetime, 4 J. INT'L LEGAL STUD. 187, 201 (1998)(using the 1983 Soviet
shootdown of KAL 007 to illustrate the higher burden of justification to use force against
civil aircraft).

are applied impartially. A neutral is not permitted, however, to impede transit
through an international strait or archipelagic sea lane.
Under the traditional law of war, belligerents have a right to seize and condemn
or destroy the ships and aircraft of the enemy, including commercial craft,131 to stop
and search neutral vessels for contraband, to close the enemy’s ports by means of a
naval blockade, and of course, to use military force against enemy warships and
military aircraft. These belligerent rights, however, may be exercised only on the
high seas or within the territorial seas of the belligerents, not within international
straits or the territorial sea of a neutral State.132
The Right of Visit and Search. During an armed conflict between States,
the warships of a belligerent State have the right to visit and search merchant ships
flying the flag of a neutral State and, if the ships are found to be carrying substantial
contraband of war to the enemy, to seize and condemn not only the contraband but
the vessels as well.133 Goods deemed to be contraband under such circumstances
clearly would include weapons of mass destruction and goods useful in their
development and production.
The right of visit and search does not extend into the territorial seas of neutral134
States or international straits overlapped by neutral territorial seas. Neutral
merchant ships are exempt if they are traveling in a convoy under the protection of
a neutral warship flying the same flag. Warships are also exempt, but it is unclear
whether other State-operated non-commercial vessels are subject to search.135
Military aircraft also have the right of visit and search.136 A military aircraft
engaged in a visit and search mission would direct a suspected vessel to the vicinity
of a friendly warship located on the high seas or within the territorial waters of a
belligerent State, allowing its crew to conduct the search, or it might direct the vessel
to a belligerent port.137 To visit and search another aircraft, the military aircraft
would escort the suspect craft to the closest belligerent landing strip.
Naval Blockades. An armed conflict could also empower a belligerent State
to set up a blockade to prevent ships of every nation from reaching its enemy’s
harbors with weapons or any other goods. The blockading State must declare the
scope of the blockade and enforce it effectively and impartially. Once a blockade is
declared, the ships of neutral States with knowledge of its existence are bound to

Whiteman, ed.,1968); 4 ENCYCLOPEDIA OF PUBLIC INTERNATIONAL LAW 409 et seq (2000)
(“Ships: Visit and Search”).
132See Fielding, supra note 45, at 1202-03.
134CDR’S HANDBOOK, supra note 51, at 388.
135Id. (citing conflicting authorities).
136Id. at 389.
137Id. at 390.

avoid the demarcated areas. Ships that attempt to run the blockade are subject to
capture and condemnation, along with their cargo.138 As an act of war carried out
during an armed conflict between States, a blockade must be asserted in conformity
to the U.N. Charter and carried out within the confines of the law of war, in
particular, the principles of military necessity and proportionality.
Air Blockade. A blockade may also be effective with respect to civil aircraft.
Civil aircraft entering a blockaded zone may be required to land for a visit and
search, and are subject to capture if they are found to be carrying contraband or
enemy personnel, are operating under enemy control, orders, charter, employment,
or direction; do not present valid documentation; or are violating regulations
established by a belligerent within the immediate area of naval operations; or are139
engaged in a breach of blockade. Another variation on the concept of a blockade
of airspace is the “no fly zone,” such as the restrictions imposed by the Security140
Council on aircraft flying over Bosnia and Herzegovina during the conflict there.
Blurring the Boundary between War and Peace
Historically, two different sets of rules applied regarding the use of force
between States; one set applied during war and another during peace. However,
since the United Nations Charter commits member States to settling their differences
peacefully and allows war only in self-defense, States have sometimes sought to carry
out acts ordinarily lawful only in the context of war, while at the same time
maintaining that they are at peace. Consequently, the boundary between peace and
war has become blurred. Some commentators argue that a new paradigm is
necessary to provide rules necessary for the protection of States’ interests in light of
these changes in the character of international conflict, the greater destructive power
of modern weapons, and the emergence of non-state actors capable of mounting
attacks against States. The following sections explore the uncertain legal boundaries
concerning the use of military force short of war.
The Right of Self Defense. The right of self-defense traditionally
recognized in international law affords a State the right to take proportionate
measures, including the use of force, that are necessary to protect itself from
imminent harm.141 Traditionally, that right included the use of force to forestall an
anticipated attack as well as to respond to an attack. As Great Britain argued in the
Caroline incident in 1837142 or, more recently, as Israel contended in seizing a ship
filled with arms bound for Palestine, that traditional right could include not only the

13878 AM. JUR. 2D, War. §§ 114, 117.
Doswald-Beck ed. 1995).
140U.N. Doc. S/RES/781 (1992).
141ENCYCLOPEDIA OF PUBLIC INTERNATIONAL LAW, supra note 131, at 361 (“Self-
De fence”).
142See International Law and the Preemptive Use of Force, CRS Report RS21314.

visit and search of a vessel but also its seizure or destruction. However, these issues
remain unsettled.
The collective security provisions of the Charter of the United Nations to some
extent have preempted the traditional right of States to use force aggressively,143 but
the Charter specifically preserves “the inherent right of individual or collective self-
defence if an armed attack occurs against a Member of the United Nations ....”144
Scholars and publicists argue about whether Article 51 affirms the traditional right
of States to act in self-defense in its entirety or, as literally read, to allow it only after
an armed attack has occurred. Yet even the more expansive reading still includes a
requirement that an attack be imminent, and for some observers, the possession of
WMD does not constitute an armed attack. Others argue that the concept of
imminence as applied to WMD may require some modification.
Circumstances might be cited in which the transport of weapons of mass
destruction poses a threat serious enough to meet that test, notably, as claimed during
the Cuban Missile Crisis (see infra). But more commonly the threat of an attack with
such weapons – particularly if they are still in the process of development – may be
distant or inchoate. To the extent that is the case, the traditional doctrine of self-
defense may not provide firm support for the use of military means to stop merchant
vessels transporting weapons of mass destruction or goods useful in the development
of such weapons outside the context of an armed conflict.145
Pacific Blockade. An exception to the notion of the blockade as an act of
war might be the so-called “pacific blockade.” Distinguished from the belligerent or
wartime blockade, pacific blockade is not intended as a belligerent act and does not
give rise to a condition of belligerency unless the State against which the action is
taken chooses to resist with force. A pacific blockade consists of naval action taken
in peacetime to apply pressure against another nation by preventing the ships of the
blockading and the blockaded nation from entering or leaving specified areas of the

14359 Stat. 1031 (1945) (Art. 39 et seq.).
144Id. art. 51.
145It might be noted that the traditional doctrine of self-defense may be a sufficient support
for naval interdiction to the extent the goods being transported are related in some fashion
to the terrorist attacks on the United States of September 11, 2001. Public Law 107-40
specifically invoked the right of self-defense as the justification for its authorization to the
President “to use all necessary and appropriate force against those nations, organizations,
or persons he determines planned, authorized, committed, or aided the terrorist attacks that
occurred on September 11, 2001, or harbored such organizations or persons ....” The
President has used that authority to employ armed force against the Taliban government in
Afghanistan and against the terrorist organization Al Qaeda and its members. Although
there may be argument over the extent to which the traditional rules regarding the use of
armed force apply to non-State actors such as Al Qaeda, it seems clear that the U.S. has had,
pursuant to its exercise of its right of self-defense under international law, a legal right to
visit, search, and possibly seize vessels owned or operated by the Taliban government as
well as those flying the flags of other States which have been carrying material aid to that
government. Moreover, it is tenable to contend that the U.S. has a similar legal right with
respect to vessels owned or operated by Al Qaeda, its members, or supporters and other
vessels suspected of providing material aid to them.

latter’s coast. The blockading State is only entitled to detain ships, not to condemn
or confiscate them or their cargo. All ships sequestered pursuant to a blockade are
to be restored to their owners when the pacific blockade is lifted.146 Traditionally, the
pacific blockade was effective only with respect to the vessels of the blockaded State;
interference with vessels of a third State is generally considered impermissible,
though practice has varied.147
Some international legal scholars have regarded the pacific blockade as lawful
only as a reprisal, i.e., an otherwise unlawful act of self-help by the blockading State
in response to an unlawful act on the part of the target State for the purpose of
achieving reparations or otherwise settling an international dispute.148 The legitimacy
of reprisals is said to depend on three conditions: that the purpose was to obtain
remedy for injury resulting from illegal action, that non-coercive methods to obtain
such remedy had failed and that the measures taken were not out of proportion to the
injury suffered.
The “quarantine” of Cuba in 1962 in response to Cuba’s procurement of
“offensive missiles” from the Soviet Union did not conform to the traditional model
of blockade, belligerent or pacific. The term “quarantine” was used to avoid the
implication that the United States intended the move as an act of war, while allowing
the United States to assert that the vessels of third States were subject to the
prohibitions. The United States did not assert the right to self defense under article
51 of the U.N. Charter as a justification for its actions.149 The strategy was successful
in averting war at the time, and appears to have been accepted as valid by the
international community; however, the euphemistic “quarantine” does not appear to
have been incorporated as a new concept in international law and it involves a
distinctive situation, e.g., Cuba was viewed as a surrogate for its supplier, the USSR.
Some observers cite U.S. reaction to the Cuban Missile Crisis as an example of
adapting international law to deal with new circumstances.150
Self-help Paradigm in International Law. Some theorists argue that the
U.N. Charter may be construed to allow the use of proportionate force to prevent
adversaries from producing, purchasing, or otherwise obtaining weapons of mass
destruction.151 Most scholars have interpreted Article 2(4) of the U.N. Charter as a
broad prohibition on any use of force against another State, except where authorized
by the Security Council acting under its Chapter VII authority, or when the use of

146See 2 OPPENHEIMS INTERNATIONAL LAW §47 (7th ed. 1952).
147See id. § 46.
148See id. §§ 33-35.
149See Schmitt, supra note 1, at 545-46.
150See id.; Fielding, supra note 45, at 1191; Guy B. Roberts, The Counterproliferation
Self-help Paradigm: A Legal Regime for Enforcing the Norm Prohibiting the Proliferation
of Weapons of Mass Destruction, 27 DENV. J. INTL L. & POLY 483, 527-29 (1999).
151For an overview of different theories that have been advanced to justify preemptive
attacks against nuclear facilities, see David Sloss, Forcible Arms Control: Preemptive
Attacks on Nuclear Facilities, 4 CHI. J. INT'L L. 39, 50 (2003) (analyzing deficiencies of
these theories).

force is justified as necessary for self-defense under Article 51.152 The alternate view
interprets the U.N. Charter prohibition on the use of force narrowly to prohibit only
certain kinds of armed attacks, namely, those “against the territorial integrity or
political independence of any State, or in any other manner inconsistent with the
Purposes of the United Nations.”153 A surgical strike against a nuclear facility in a
proliferant State, so the argument goes, would threaten neither the territorial integrity
nor the political independence of a target State, inasmuch as there would be no effort
to annex or occupy territory, nor overthrow the current political leadership.154 The
legitimacy of a preventive attack against WMD or their components would rest on
an interpretation of whether their destruction comports with the “purpose of the
United Nations.”
To the extent that the elimination of WMD in the hands of a perceived unstable
State may be seen to enhance international peace and security by promoting
disarmament, some argue that an otherwise unlawful attack might be justifiable. For
example, Israel’s 1981 aerial bombardment of an Iraqi nuclear power facility, while
condemned by the U.N. Security Council,155 was viewed by some as justifiable under
international law and the U.N. Charter.156 Others argue, however, that the U.N.
Charter created the Security Council and entrusted collective security decisions
primarily to that body, leaving to member States the inherent right to defend
themselves only in case of an armed attack.157 According to that view, the role of the
Security Council under the Charter and self-defense provision in article 51 seem to
contradict a narrow interpretation of article 2(4)158 that would allow each State to
decide for itself when a contemplated use of force is within the purpose of the United
Some argue that, whatever the original intent of the U.N. Charter, States’
practice since 1945 has shown the prohibition against the use of force to exist only
on paper, and voluntary compliance with non-proliferation regimes cannot be
counted on to rein in proliferant States and do not in any event apply to non-State
actors bent on obtaining WMD. Proponents of this view urge the world community
to adopt a paradigm shift that would revert to pre-U.N. concepts of international

152See Timothy Kearley, Regulation of Preventive and Preemptive Force in the United
Nations Charter: A Search for Original Intent, 3 WYO. L. REV. 663, 670 (2003).
153U.N. Charter art. 2(4).
154But see Sloss, supra note 151, at 50-51(noting that the “broad interpretation” – holding
that all transboundary acts of force are prohibited unless in self-defense or under authority
of the U.N.S.C. – is prevalent among scholars).
155U.N. Doc. S/RES/487 (1981).
156See Anthony D'Amato, Israel's Air Strike Upon the Iraqi Nuclear Reactor, 77 AM J INTL
L 584, 586 (1983)(arguing the sheer destructive force of nuclear weapons may have justified
a limited attack even where a similar attack to destroy conventional weapons would not have
been justified). Israel asserted that it was in a state of war with Iraq, justifying the air strike
as an act of self defense. See Schmitt, supra note 1, at 546.
157See Kearley, supra note 152, at 670 (examination of the intent behind the U.N. Charter).
158See Sloss, supra note 151, at 53.

relations, in which nations with sufficient strength were understood to have the
power to take self-help measures, including the use of force, to right international
wrongs and enforce compliance with international law.159 Under this view, States
would be justified in using preventive or preemptive force to deter plans to acquire
WMD, eliminate acquisition programs or destroy WMD components or sites at any
stage in the acquisition effort.160
The “counterproliferation self-help paradigm” is based on the assumption that
non-proliferation has become so entrenched in international law that it has reached
the status of customary norm,161 binding on all States whether or not they have
agreed, by joining the relevant treaties, to desist from developing or acquiring
WMD.162 Under this view, any State that persists in the development or acquisition
of WMD, or permits its citizens and residents to do so with impunity, is committing
a wrongful act under international law for which other States may demand redress.
Thus, although States Parties retained the right to withdraw from the treaties upon
giving notice, participation in the various non-prolifereration regimes, under this
view, has become jus cogens – a mandatory and enforceable requirement of
international law.163
There is some evidence that might support the argument that nonproliferation
has become a customary norm.164 For example, the number of States that have
agreed to participate in the nonproliferation regimes provides an indication of the
near universal support for them. Furthermore, in making the argument that
international law supports the PSI, the Bush Administration cited a statement by the
President of the U.N. Security Council in 1992 indicating that the Council considers
proliferation of WMD to be a matter that poses a threat to international peace and
security.165 With respect to disarmament, arms control and weapons of mass
destruction, the 1992 Statement said
The members of the Council, while fully conscious of the
responsibilities of other organs of the United Nations in the fields of

159See generally Roberts, supra note 150.
160See id. at 485.
161Customary norms develop from “a general and consistent practice of states followed by
them from a sense of legal obligation.” See RESTATEMENT, supra note 39, § 102.
162See Roberts, supra note 150, at 499-500 (arguing that “institution building has helped to
create and extend an overall norm of non- proliferation – one that is arguably jus cogens.
That is, a pre-emptory norm of international law...”).
163See RESTATEMENT, supra note 39, § 102 comment k (defining jus cogens, or peremptory
norms of international law as rules recognized by the international community as non-
derogable). Although it is widely accepted that such a category of international law exists,
its content is not agreed. See id. reporter’s note 6.
164See PSI Fact Sheet, supra note 126 (“The increasingly aggressive efforts by proliferators
to stand outside or to circumvent existing nonproliferation norms, and to profit from such
trade, requires new and stronger actions by the international community.”).
165See id. (arguing PSI is “consistent with and a step in the implementation of the UN
Security Council Presidential Statement...”).

disarmament, arms control and non-proliferation, reaffirm the crucial
contribution which progress in these areas can make to the
maintenance of international peace and security. They express their
commitment to take concrete steps to enhance the effectiveness of the
United Nations in these areas.
The members of the Council underline the need for all Member States
to fulfil their obligations in relation to arms control and disarmament;
to prevent the proliferation in all its aspects of all weapons of mass
destruction; to avoid excessive and destabilizing accumulations and
transfers of arms; and to resolve peacefully in accordance with the
Charter any problems concerning these matters threatening or
disrupting the maintenance of regional and global stability. They
emphasize the importance of the early ratification and implementation
by the States concerned of all international and regional arms control
arrangements, especially the START and CFE Treaties.
The proliferation of all weapons of mass destruction constitutes a
threat to international peace and security. The members of the
Council commit themselves to working to prevent the spread of
technology related to the research for or production of such weapons
and to take appropriate action to that end.
On nuclear proliferation, they note the importance of the decision of
many countries to adhere to the Non-Proliferation Treaty and
emphasize the integral role in the implementation of that Treaty of
fully effective IAEA safeguards, as well as the importance of
effective export controls. The members of the Council will take
appropriate measures in the case of any violations notified to them by
the IAEA.
On chemical weapons, they support the efforts of the Geneva
Conference with a view to reaching agreement on the conclusion, by
the end of 1992, of a universal convention, including a verification
regime, to prohibit chemical weapons.
On conventional armaments, they note the General Assembly's vote
in favour of a United Nations register of arms transfers as a first step,
and in this connection recognize the importance of all States
providing all the information called for in the General Assembly's166
The Bush Administration also points to positions taken by other international
coalitions that may lend some support to the broad notion that nonproliferation is
approaching jus cogens status. In June, 2002, in response to the threat of terrorist
groups obtaining and using WMD, the G8 Leaders announced a new “G8 Global

166See Statement of the U.K. Prime Minister (John Major) at a summit-level meeting of the
Security Council on 31 January 1992 on the maintenance of international peace and security,
U.N. Doc. S/23500 (1992), reprinted at 31 I.L.M. 758 (1992).

Partnership Against the Spread of Weapons and Materials of Mass Destruction.”167
The European Union published a set of principles June 10, 2003 for addressing the
global threat of WMD, noting that
To address the new threats, a broad approach is needed. Political and diplomatic
preventative measures (multilateral treaties and export control regimes) and
resort to the competent international organisations (IAEA, OPCW, etc.) form
the first line of defence. When these measures (including political dialogue
and diplomatic pressure) have failed, coercive measures under Chapter VII of
the UN Charter and international law (sanctions, selective or global,
interceptions of shipments and, as appropriate, the use of force) could be168
envisioned. The UN Security Council should play a central role.
Finally, some suggest that the Proliferation Security Initiative may also serve as
evidence of the progression of international law with regard to WMD,169 although it
remains to be seen what actions it will entail and how other nations might react to its
However, these international developments may not provide evidence sufficient
to prove that nonproliferation has emerged as a non-derogable norm. Notably, the
statement by the U.N. Security Council excerpted above may be read as a promise
to take action, but does not say what action the Security Council might take, and does
not authorize States to enforce treaty commitments on the part of other States. It
calls upon States to adhere to their treaty commitments and cooperate toward further
international negotiations related to arms control. Moreover, as a statement rather
than a formally adopted resolution, it has less binding force on member States under
the U.N. Charter. Finally, States’ practice does not appear unambiguously to
demonstrate that States consider themselves bound to halt all activity with regard to
WMD testing, production or transfer.
The argument that nonproliferation has achieved the status of customary
international law seems more plausible with respect to chemical and biological
WMD than with respect to nuclear weapons, since the relevant treaties prohibit all
possession, trade, and use of such weapons by member States, and require member
States to adopt laws criminalizing the possession of banned materials. Nuclear

167Statement by G8 Leaders, The G8 Global Partnership Against the Spread of Weapons and
Materials of Mass Destruction, Kananaskis, June 27, 2002, available at
[ h t t p : / / www.dt .tesoro.it/Aree-Docum/ Rel a zi oni -/ G7-e -gl i -a/ G7/ Document a z/ 2002/ St at e
ment-Global-Partnership.pdf] (last visited Sep. 8, 2003).
168Council of The European Union, Basic Principles for an EU Strategy against
Proliferation of Weapons of Mass Destruction, Doc. 10352/03, Brussels (June 10, 2003),
at para. 4, available at [http://register.consilium.eu.int/pdf/en/ 03/st10/st10352en03.pdf (last
visited Sep. 11, 2003)[hereinafter “EU Strategy”].
169See Robert Chesney, The Proliferation Initiative and WMD Interdiction on the High Seas,
NATIONAL STRATEGY FORUM (Fall 2003), available at
[http://www.nationalstrategy.com/Fall%20NSFR%202003/Chesney.htm] (noting that “PSI
itself might mark an important development in the evolution of ... an exception [to free
navi gation]”).

weapons, however, are not universally banned.170 The NPT allows five States to
stockpile nuclear weapons, and leaves it to their discretion as to whether possession
on the part of their sub-national groups is criminalized under the national laws of
member States.171 This inconsistency appears to make the argument that the State
possession of nuclear weapons is a jus cogens violation less tenable.172
Others view the non-proliferation regimes to be more in the nature of a security
pact, with weaker nations having agreed to forego WMD programs in exchange for
a promise of security to be provided through alliance with one of the great powers,
rather than evidence that States participate out of a sense of legal obligation. Part of
the bargain, with respect to nuclear weapons, was that the five nuclear powers
negotiate to bring about an eventual total disarmament.173 Now that the mutual
deterrence of the Cold War can no longer be said to be in operation, non-nuclear
States may believe their security requirements have increased, or that the strategic
value of possessing nuclear weapons outweighs the benefit of remaining party to the
NP T. 174
Collective Action Under Security Council Mandate. Adherents of the
“broad” interpretation of the U.N. Charter prohibition against the use of force are
more likely to view preemptive use of military force against WMD facilities,
including the interdiction of ships suspected of transporting elements of an
unauthorized nuclear weapons program, to be legitimate only when the U.N. Security175
Council specifically authorizes it. Under the U.N. Charter, the Security Council
has “primary responsibility for the maintenance of international peace and176
security.” In this view, the Security Council is better empowered to determine that

170See Barry Kellman, WMD Proliferation: An International Crime?, NONPROLIFERATION
REV., Summer 2001, at 93, 98 (arguing that “the discriminatory structure of the NPT
undermines any argument that state possession of WMD is necessarily a crime”).
171See id.
172See RESTATEMENT, supra note 39, § 102, reporter’s note 6 (noting that some authorities
suggest that treaties that create international crimes and obligate all states to proceed against
violations may be peremptory).
173See Nuclear Nonproliferation Issues, CRS Issue Brief IB10091, at CRS-4-5.
174In 1996, several non-nuclear States adopted a Statement of Principles and Objectives that
would pledge the NPT state-parties to work toward several primary objectives, including
universalization of NPT membership and adherence, a reaffirmation of the commitment of
the nuclear weapon States to pursue measures toward eventual complete nuclear
disarmament, the completion of the Comprehensive Test Ban Treaty (CTBT) by the end of
1996, and other steps to assure the non-nuclear weapon States against the use or threat of
use of nuclear weapons. See Ambassador Thomas Graham, Jr., International Law and the
Proliferation of Nuclear Weapons, 33 GEO. WASH. INT'L L. REV. 49, 55-56 (2000).
175See Schmitt, supra note 1, at 526 (noting that the Security Council has a mandate to
counter threats to the peace as well as actual uses of force, and that it may order
enforcement action to maintain international peace and security as well as restore them);
Sloss, supra note 151, at 52-54.
176United Nations Charter, art 24(1).

WMD in the hands of only certain States and non-State actors constitutes a threat to
the peace, tailoring an enforcement regime against those entities.
The Security Council has multiple options for dealing with a threat it has
identified, including economic sanctions, interdiction of weapons, and the use of
military force through the forces of member States.177 It also has some options with
respect to enforcement.178 Under its Chapter VII authority it could authorize a
coalition of member States to organize and lead a force to carry out a specific
mandate, or it could authorize an organization such as NATO to enforce the action.
Another option would entail the creation of a U.N. military force, similar to the U.N.
Mission to Sierra Leone.179 In any case, nine “yes” votes from the U.N. Security
Council are needed, with none of the five permanent members exercising their veto.
International law recognizes that States have the right to interdict vessels and
aircraft in certain limited circumstances; however, that legal authority exists that
would allow PSI nations completely “to halt shipments of dangerous technologies to
and from states and non-state actors of proliferation concern – at sea, in the air, and
on land”180 appears doubtful under the current state of international law. The United
States and its allies may consider whether to amend the treaties regarding the law of
the sea (and air) explicitly to include WMD and missile trade within the prohibitions
that may be universally enforced. Other options include amending the proliferation
treaties to enhance compliance and, as the European Union stressed in its statement
of non-proliferation principles, to reduce the perception among States that WMD are
necessary for their own security.181 Probably the firmest legal basis for interdicting

177U.N. CHARTER art. 42 states:
Should the Security Council consider that measures provided for in Article 41
[non-forceful sanctions] would be inadequate or have proved to be inadequate, it may take
such action by air, sea, or land forces as may be necessary to maintain or restore
international peace and security. Such action may include demonstrations, blockade, and
other operations by air, sea, or land forces of Members of the United Nations.
178See Schmitt, supra note 1, at 527.
179See id.; U.N. Doc. S/RES/1289 (2000).
180White House Press Release, Principles for the Proliferation Security Initiative, Sep.4,

2003, available at [http://www.state.gov/t/np/rls/prsrl/23809.htm] (last visited Sep.8, 2003).

181See EU Strategy, supra note 168, para. 8:
The best solution to the problem of proliferation of WMD is that countries should no
longer feel they need them. If possible, political solutions should be found to the
problems which lead them to seek WMD. The more secure countries feel, the more
likely they are to abandon programmes: disarmament measures can lead to a virtuous
circle just as weapons programmes can lead to an arms race. To this end, we must
actively foster the establishment of regional security arrangements and regional arms
control and disarmament processes. Our dialogue with the countries concerned should
take account of the fact that in many cases they have real and legitimate security
concerns, with the clear understanding that there can never be any justification for the
illegal development of WMD. . . .

WMD materials would be provided by explicit authorization by the U.N. Security

Appendix A – Interdiction Principles for the
Proliferation Security Initiative
PSI participants are committed to the following interdiction principles to establish
a more coordinated and effective basis through which to impede and stop shipments
of WMD, delivery systems, and related materials flowing to and from states and
non-state actors of proliferation concern, consistent with national legal authorities
and relevant international law and frameworks, including the UN Security Council.
They call on all states concerned with this threat to international peace and security
to join in similarly committing to:
1.Undertake effective measures, either alone or in concert with other states, for
interdicting the transfer or transport of WMD, their delivery systems, and
related materials to and from states and non-state actors of proliferation concern.
“States or non-state actors of proliferation concern” generally refers to those
countries or entities that the PSI participants involved establish should be
subject to interdiction activities because they are engaged in proliferation
through: (1) efforts to develop or acquire chemical, biological, or nuclear
weapons and associated delivery systems; or (2) transfers (either selling,
receiving, or facilitating) of WMD, their delivery systems, or related materials.
2.Adopt streamlined procedures for rapid exchange of relevant information
concerning suspected proliferation activity, protecting the confidential character
of classified information provided by other states as part of this initiative,
dedicate appropriate resources and efforts to interdiction operations and
capabilities, and maximize coordination among participants in interdiction
3.Review and work to strengthen their relevant national legal authorities where
necessary to accomplish these objectives, and work to strengthen when
necessary relevant international law and frameworks in appropriate ways to
support these commitments.
4.Take specific actions in support of interdiction efforts regarding cargoes of
WMD, their delivery systems, or related materials, to the extent their national
legal authorities permit and consistent with their obligations under international
law and frameworks, to include:
a.Not to transport or assist in the transport of any such cargoes to or from
states or non-state actors of proliferation concern, and not to allow any
persons subject to their jurisdiction to do so.
b.At their own initiative, or at the request and good cause shown by another
state, to take action to board and search any vessel flying their flag in their
internal waters or territorial seas, or areas beyond the territorial seas of any
other state, that is reasonably suspected of transporting such cargoes to or
from states or non-state actors of proliferation concern, and to seize such
cargoes that are identified.

c.To seriously consider providing consent under the appropriate
circumstances to the boarding and searching of its own flag vessels by
other states, and to the seizure of such WMD-related cargoes in such
vessels that may be identified by such states.
d.To take appropriate actions to (1) stop and/or search in their internal
waters, territorial seas, or contiguous zones (when declared) vessels that
are reasonably suspected of carrying such cargoes to or from states or
non-state actors of proliferation concern and to seize such cargoes that are
identified; and (2) to enforce conditions on vessels entering or leaving their
ports, internal waters or territorial seas that are reasonably suspected of
carrying such cargoes, such as requiring that such vessels be subject to
boarding, search, and seizure of such cargoes prior to entry.
e.At their own initiative or upon the request and good cause shown by
another state, to (a) require aircraft that are reasonably suspected of
carrying such cargoes to or from states or non-state actors of proliferation
concern and that are transiting their airspace to land for inspection and
seize any such cargoes that are identified; and/or (b) deny aircraft
reasonably suspected of carrying such cargoes transit rights through their
airspace in advance of such flights.
f.If their ports, airfields, or other facilities are used as transshipment points
for shipment of such cargoes to or from states or non-state actors of
proliferation concern, to inspect vessels, aircraft, or other modes of
transport reasonably suspected of carrying such cargoes, and to seize such
cargoes that are identified.
Source: White House Fact Sheet, Sep. 4, 2003, available at
[ ht t p: / / www.whi t e house.gov/ news/ r el eases/ 2003/ 09/ 20030904-11.ht ml ] .