Weapons of Mass Destruction Counterproliferation: Legal Issues for Ships and Aircraft
Released: 2003-10-01T00:00:00

Summary:
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 combinesefforts aimed at counterproliferation, nonproliferation, and WMD consequence management. Theintent, it says, is to eliminate or "roll back" WMD in the possession of certain States and terroristgroups, including potentially the use of force and aggressive methods of interdiction ofWMD-related goods, technologies, and expertise. The use of interdiction as a counterproliferationmeasure appears to be part of a strategy that foresees the U.S. taking "anticipatory action to defendourselves" against terrorists and rogue States, "even if uncertainty remains as to the time and placeof the enemy's attack," and "to detect and destroy an adversary's WMD assets before these weaponsare 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 weaponsand related technologies "at sea, in the air, and on land." However, the Administration hasrecognized that cooperation may not always be forthcoming, and has intimated that it will actunilaterally, 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 aviationagreements. The right of States to conduct self-defense and law enforcement activities abroad hasthe potential to collide with the rights of other States to maintain their sovereign integrity andconduct free navigation and commerce. These rights are not absolute. This report provides anoverview of the international law of the sea and other agreements as they relate to the permissiblerange of methods for interdicting WMD-related contraband. After a short summary of the currentlegal regime for international arms control related to WMD, the report outlines the basic conceptsof 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 conducttakes place. The report then turns to the international legal framework limiting the conduct ofnations as it applies during times of war and peace, and during what has been called "quasi war."

subsections: section_title: Introduction
paragraphs: 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 whichnot only any nation, but sub-national groups as well, may be able to acquire weapons of massdestruction (WMD). Strategies based on containment and deterrence, it is argued, are insufficientto guarantee security in the twenty-first century threat environment; terrorists and "rogue" nationsare 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 UnitedStates of America issued in September, 2002. (2) According to the Bush Administration, in order tostrengthen nonproliferation efforts to prevent rogue States and terrorists from acquiring weapons ofmass destruction,
[w]e will enhance diplomacy, arms control, multilateral export controls, and threat reduction assistance that impede states and terrorists seeking WMD, andwhen necessary, interdict enabling technologies and materials. (3)
Toward that end, President Bush issued his National Strategy to Combat Weapons of MassDestruction in December, 2002. The Administration's plan combines efforts aimed atcounterproliferation, (4) nonproliferation, and WMDconsequence management. Its purported intentis to eliminate or "roll back" WMD from certain states and terrorist groups who possess suchweapons or are close to acquiring them, including potentially the use of force and aggressivemethods of interdiction of WMD-related goods, technologies, and expertise. (5) The use of interdictionas 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 uncertaintyremains as to the time and place of the enemy's attack," (6) and "to detect and destroy an adversary'sWMD 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 impedimentsto the strategy. Acting on intelligence from the United States, a Spanish frigate stopped and boardedthe 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 vesselto proceed on its voyage. The Bush Administration concluded that there was no legal basis to arrestthe 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 isan effort to reach agreements among nations toallow searches of ships and aircraft carrying suspected weapons-related cargo. (10) Undersecretary ofState 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 inconcert, 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 relatedequipment 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 destructiveweapons away from our shores and out of the hands of our enemies. We aim ultimately, not just toprevent the spread of weapons of mass destruction, but also to eliminate or roll back such weaponsfrom rogue states and terrorist groups that already possess them or are close to doing so. (11)
Rather than seeking to change existing treaties or negotiate new ones, the PSI appears to relyon international agreements that will enhance cooperation in interdiction efforts, including sharinginformation and conducting exercises using military or civilian assets to develop the participatingnations' ability to conduct air, ground, and maritime interception. (12) However, recognizing thatcooperation may not always be forthcoming from all nations whose assistance is requested, theAdministration has intimated that it will act unilaterally, if necessary. (13)
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 enforcementactivities abroad, insofar as some activities could be viewed as unwarranted or unlawful interferencewith the rights of other nations to conduct international commerce and maintain sovereignty overtheir territory. This report provides an overview of the international law of the sea as it relates to thepermissible range of methods for interdicting WMD-related contraband on the sea and in the air, andalso of selected pertinent international regimes and agreements. After a short outline of the currentlegal regime for the international control of WMD, the report outlines the basic concepts ofjurisdiction 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 theconduct 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. 
section_title: Weapons of Mass Destruction - International Legal Regime
paragraphs: From a U.S. perspective, the problem of controlling the proliferation of WMD is particularlythorny because, unlike the control of illicit drugs, it does not suffice to keep the materials fromentering the United States or to prevent their manufacture and dispersal on U.S. territory. Completesecurity from the dangers of a WMD attack would require that dangerous materials be kept out ofthe hands of any potential enemy. Moreover, some materials that can be used in the production ofWMD also have peaceful uses, and may even be necessary for the operation of wholly legitimateindustries. Interference in the trade of "dual use" materials could impair the ability of other Statesto carry out legitimate trade, possibly leading to international discord. Finally, under internationallaw, sovereign States have the right in general to possess weapons for their self-defense. Only theuse of such weapons is constricted by customary international law. (14) While many States have agreedto limit their production and possession of some types of WMD and conventional weapons, they mayhave conditioned their consent on the conduct of other States, and may be able to revoke theirconsent in accordance with any such conditional agreement. While secret development of WMDon the part of a State that has agreed not to engage in such conduct would constitute a breach of atreaty obligation, it is not necessarily a crime or an act of aggression under international law merelyto possess such weapons.
subsections: section_title: Nuclear Weapons
paragraphs: The center of the nuclear nonproliferation regime is the Nuclear Nonproliferation Treaty ("NPT"). (15) The treaty defines nuclear weaponsStates as those States that had manufactured anddetonated 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 nuclearweapons, but prohibits the transfer of such weapons to other States. (17) All other States Parties to theNPT have agreed not to acquire nuclear weapons in return for assistance in developing peaceful usesfor nuclear power. (18) The five declared nuclearpowers are committed under the treaty to "pursuenegotiations in good faith on effective measures relating to cessation of the nuclear arms race at anearly date and to nuclear disarmament, and on a treaty on general and complete disarmament understrict and effective international control." (19) StatesParties may withdraw from the NPT on threemonths' notice if "extraordinary events, related to the subject matter of [the NPT], have jeopardizedthe 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 nuclearmaterial, provided that the nuclear material is subject to IAEA safeguards. Each non-nuclear StateParty is required to negotiate a set of safeguards for verification and accounting of nuclear materialsat its declared nuclear sites. No State Party is permitted to transfer nuclear materials or equipmentfor processing them to any non-nuclear State for peaceful purposes unless the transferred goods aresubject to IAEA safeguards. (21) The IAEA isempowered to conduct "special inspections" if a StateParty reports a loss of inspected material, but is not empowered to take any action if it suspects thatclandestine nuclear programs are taking place at undisclosed sites. In the event it discovers aviolation, the IAEA is to report the noncompliance to the U.N. Security Council and GeneralAssembly, as with other arms control agreements. Neither the NPT nor IAEA regulations providesfor 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 multilateralexport control groups in order to coordinate nonproliferation efforts. (24) These groups harmonize listsof sensitive materials and technologies that must be controlled in order to prevent proliferation ofnuclear weapons and methods by which member countries are to prevent their transfer. Regimemembers agree to restrict such trade by implementing laws, regulations, and licensing requirementsapplicable to citizens and residents. They may also agree to share information about exports andlicenses. The regimes are voluntary and non-binding. (25)
section_title: Chemical Weapons
paragraphs: 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 ofpoison or poisoned weapons. (26) The 1925 GenevaProtocol prohibited the use of asphyxiating,poisonous, or other gases, all analogous liquids, materials or devices, and bacteriological methodsof warfare. (27) The first convention to prohibit themanufacture and stockpiling of chemical weaponsis the Chemical Weapons Convention ("CWC"). (28) The CWC calls for all State Parties to eliminatetheir chemical weapons supplies by 2007 and restrict their trade in "precursors" - chemicals that canbe used in the production of weapons as well as for peaceful uses - to other States Parties. StatesParties agree to cease production and stockpiling of weapons, declare all facilities that producerestricted chemicals for non-prohibited uses, submit to verification inspections, and pass legislationimplementing 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 routineinspections of the relevant facilities on the territory of States Parties to verify the accuracy of annualdeclarations regarding scheduled chemicals. The OPCW may also carry out a "challenge" inspectionin response to allegations of noncompliance by one State Party with respect to another. TheConference of States Parties addresses concerns over noncompliance, but other than requesting abreaching member to comply or requesting action on the part of the U.N. Security Council, the extentof remedial measures that might be imposed by the Conference is not defined. (30)
section_title: Biological Weapons
paragraphs: Biological weapons were first addressed in the Geneva Protocol of 1925, (31) which banned onlytheir use and not their manufacture, stockpiling, or transfer to other States. The Biological WeaponsConvention ("BWC") (32) addresses thedevelopment, production, acquisition, or stockpiling of"[m]icrobial or other biological agents, or toxins whatever their origin or method of production, oftypes and in quantities that have no justification for prophylactic, protective or other peacefulpurposes" as well as "[w]eapons, equipment or means of delivery designed to use such agents ortoxins for hostile purposes or in armed conflict." (33) States Parties to the BWC undertake to prohibitthe above conduct, destroy biological weapons supplies already on hand, and "not to transfer to anyrecipient whatsoever, directly or indirectly, and not in any way to assist, encourage, or induce anyState, group of States or international organizations to manufacture or otherwise acquire any of theagents, toxins, weapons, equipment or means of delivery specified in article I of [the BWC]." (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 compliancebased on the model of the CWC. (35) The BushAdministration rejected the BWC Protocol while it wasbeing drafted, objecting to its "approaches to the issue." (36) A State Party that believes another StateParty to be in breach of its obligations may complain and present evidence to the U.N. SecurityCouncil. The Security Council may initiate an investigation, with which the accused is bound tocooperate, (37) but no further remedial measures arespecified. States may withdraw from the BWC onthree months' notice. (38)
section_title: Limitation on Enforcement
paragraphs: 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 onlyapply to States that choose to join them and remain party to them. Non-member States may havedifficulty procuring WMD-related technology and materials from States Parties to the respectivetreaties, but may trade freely among themselves and are under no legal bounds to refrain fromstockpiling such weapons or transferring them to terrorist organizations and other entities, or fromconducting research to develop new ones. States Parties participate on a voluntary basis, and maychoose to back out of the conventions at any time, as was the case when North Korea backed out ofthe NPT. The success of the arrangements depends on the cooperation of member States and theirability and willingness to enforce their own laws prohibiting acquisitions and exports ofWMD-related materials.
section_title: Jurisdiction under International Law
paragraphs: 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 ofinternational law. Each State is independent and has supreme authority over its territory and generalauthority over its citizens. The term "jurisdiction" refers to the authority of the State to affect thelegal interests of individuals and entities. Jurisdiction may describe a State's authority to make itslaw applicable to certain actors, events, or things (jurisdiction to prescribe); a State's authority tosubject certain persons or things to the processes of its courts (jurisdiction to adjudicate); or a State'sauthority 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 thejurisdiction 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 havea claim to jurisdiction over a matter. Historically, the most commonly asserted basis for jurisdictionis the "territoriality principle" (determining jurisdiction by reference to the place where the offenseis committed). (40) Other bases of jurisdictioninclude the "nationality principle" (determiningjurisdiction 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 theoffense); and the "passive personality principle" (determining jurisdiction by reference to thenationality 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. Statesmay also exercise extraterritorial jurisdiction under certain circumstances, but in general, this doesnot 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 thatoccurred outside of its territory that did not involve any of its nationals, but the scope of universaljurisdiction is not well-settled, and may not include the authority to take enforcement action on theterritory of another state without its permission. At any rate, the possession or delivery of WMD orrelated materials is not generally recognized as a crime subject to universal jurisdiction, like suchinternational 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 innocentpassage, (42) within its territorial waters and airspace. The United States can also place restrictions onthe conduct of U.S. citizens anywhere in the world (43) with regard to WMD under the principle ofnationality; (44) however, that authority does notencompass a right to carry out law enforcementactivities in another State without its permission. Furthermore, if U.S. law enforcement or militaryforces encounter WMD trade outside the territory of the United States, even if the activity isunlawful under the laws of the State where it takes place or violates the international obligations ofany State, there is no automatic authority under international law for U.S. forces to take action tothwart 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 relevantmultilateral or bilateral agreements the United States has entered into. Specific instances determinedby the United Nations Security Council to constitute aggression or a threat to international peace andsecurity may be dealt with through action under Chapter VII of the U.N. Charter. (45) Specific threatsto the United States that amount to an armed attack or imminent threat of an armed attack may justifya belligerent response, such as the implementation of a blockade or the use of armed force in selfdefense. Such a response could draw reactions from other States and possibly escalate into afull-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 enforcementactivity 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 besubject to that State's terms of agreement or willingness and capacity to resist. Enforcement actionin places where no State has sovereign authority, such as the high seas, may meet with relatively lightresistance from other States, but remains subject to international law. 
section_title: The Law of the Sea
paragraphs: The law of the sea divides authority among nations to conduct activity in or above the oceansand external waterways that both divide and connect nations. The basic rules of international lawwith respect to jurisdiction over vessels on the high seas are set forth in the Convention on the HighSeas (46) and the more recent United Nations Lawof the Sea Convention (UNCLOS). (47) The UnitedStates 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 navigation and the uses of theoceans "generally confirm existing maritime law and practice and fairly balance the interests of allstates." (49) Both conventions affirm that the highseas are open to all States, that freedom ofnavigation is a basic freedom of the high seas, and that every State has "the right to sail ships underits flag on the high seas." (50) The law of the seabalances the rights of maritime States to navigatefreely with the rights of coastal States to maintain security. It also deals with some aspects of airtransportation, applying to aircraft some, but not all, of the rules that apply to maritime vessels.
subsections: section_title: Legal Divisions of Waters
paragraphs: 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 thewaters determines the rights and obligations of Statesand their vessels, public and private. National waters include internal waters (lakes and rivers, someharbors and bays, and other waters that lie between the actual shoreline and the claimed baseline (52) )of a coastal State and its territorial sea. The State has complete sovereign control over internalwaters, and consent must be given for any vessel to enter or for aircraft to fly over it except in casesof emergency. (53) Any private vessel that entersthe internal waters of a coastal State is subject to thejurisdiction of that State and may be stopped and searched by military or law enforcement personnelin 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 thebaseline as its territorial sea. (54) A State mayexercise sovereignty over its territorial sea, but its rightsare subject to foreign vessels' right of innocent passage . UNCLOS provides that foreign flaggedvessels have the right of unimpeded passage through the territorial sea of a coastal State providedpassage is "innocent," meaning the ship's conduct is "not prejudicial to the peace, good order orsecurity of the coastal State" and takes place in conformity with international law. (55) The right ofinnocent passage does not apply to aircraft. Conduct that is considered prejudicial includes militaryexercises, launching of aircraft or weapons, intelligence collection, research, fishing, or dumpingpollutants. (56) Submarines must remain on thesurface 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 worthnoting that cargo, destination, or ultimate purpose are not among the criteria to be used to determinewhether passage is innocent. (59)
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, areimplemented in a non-discriminatory fashion, and do not have the practical effect of denying orimpairing the right of innocent passage. While the conventions do not require notification orpermission 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 UnitedStates takes the position that such measures do not comport with the law of the sea, and frequentlycarries out Freedom of Navigation (FON) exercises to demonstrate its non-acquiescence to theclaimed rights. (61)
Contiguous Zones and Exclusive Economic Zones (EEZ). The Conventions also recognize that every coastal State may lay morelimited claim to a number of maritime zones in the international waters extending beyond theterritorial 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 toprevent and punish infringements of the customs, fiscal, immigration, and sanitary laws andregulations that apply in its territorial sea. The contiguous zone may extend up to 24 miles from thecoast. Up to 200 miles from the coast may be claimed as an Exclusive Economic Zone (EEZ), inwhich the coastal State may exploit the natural resources. For the purpose of exercising jurisdictionto enforce the law, the areas beyond the territorial sea of any coastal State are treated as the high seas. 
Straits. Straits overlapped by the territorial seas of coastal nations that are used for international navigation from one part of the high seas or anexclusive economic zone to another similar area are subject to a special regime different from thatof ordinary territorial seas, known as transit passage . (62) The vessels and aircraft of all nations havethe right to unimpeded transit through the straits in their ordinary mode of travel (submarines mayremain submerged). Ships and aircraft navigating through straits must proceed without delay, mustrefrain from using or threatening to use force, and may not engage in any activities other than thoseincident to their normal and expeditious travel. (63) Coastal nations may not suspend or hamper theright of transit when they are not at war, even with respect to warships of belligerent nations at warwith others. (64) However, coastal States mayimpose requirements for safe navigation, such asrequiring ships to use delineated shipping lanes. (65) Archipelagic waters are treated similarly. (66)
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 includedin 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 toits sovereignty." The ships of all nations, whether coastal or land-locked, enjoy the freedom tonavigate, fish, and lay pipelines or cables. (68) UNCLOS adds two new freedoms: to conduct scientificresearch 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 exerciseof the freedom of the high seas, and also with due regard for the rights under this Convention withrespect to activities in the Area." (70)
section_title: Legal Status of Vessels
paragraphs: 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, onthe high seas, a ship is under the "exclusive jurisdiction" of the State whose flag it flies. (71) Warshipsand State-owned or operated vessels "used only on government non-commercial service" are saidto enjoy "complete immunity" from the jurisdiction of non-flag States. (72) Merchant ships, on theother hand, are subject to a number of exceptions to exclusive flag State jurisdiction. 
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] shipmay not change its flag during a voyage or while in a port of call, save in the case of a real transferof ownership or change of its registry." (73) Bothfurther mandate that every State "shall fix theconditions for the grant of its nationality to ships, for the registration of ships in its territory, and forthe right to fly its flag." (74) States may maintain"open registries" of vessels, meaning a foreignnational may register a vessel and have the right to fly that States flag as a "flag of convenience,"enjoying the protection of that State. (75) A ship thatflies the flags of two or more States, or that fliesno 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 commissionedofficer 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 otherStates on the high seas or in territorial seas. Police and port authorities may only board a warshipwith the permission of the Commanding Officer. Warships are exempt from foreign regulations butare bound to comply with established principles of international law. A warship is in effect thesovereign 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 coastalState to leave its territorial waters, and is bound to comply with such a request. (77)
section_title: Airspace and Aircraft
paragraphs: Prior to the advent of the airplane, the concept of sovereignty primarily concerned rights overland and sea. As aerospace technologies developed at the start of the twentieth century, making itpossible for nations to exert some actual control over activities in the skies above them, the conceptof exclusive sovereignty over airspace super-adjacent to the territory of a State quickly coalesced intocustomary international law. (78) While freedom ofnavigation for commercial purposes was supportedin 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 beendeveloped through treaty. (80)
Law of the Sea Conventions. Where airspace istreated in the conventions on the law of the sea, it is generally divided into national and internationalairspace, with national airspace including that above the territorial sea. There is no right of innocentpassage for overflight of the territorial sea of a coastal State, but the rules of transit passage overstraits and archipelagic waters apply to aircraft as well as ships, even though the airspace isconsidered national. The Convention on the High Seas includes the airspace above internationalwaters in the freedom to navigate. (81) It is unclearwhether rights and privileges accorded to "ships"extend by analogy to aircraft where the conventions do not specifically address them, such as theright 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 completeand exclusive sovereignty over the airspace above its territory." (83) "Territory" includes the territorialseas. (84) Presumably, all non-territorial airspaceis 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 someduties and restrictions on them. Article 3 states that "[n]o state aircraft ... shall fly over the territoryof another State or land thereon without authorization..." Contracting States commit to "hav[ing] dueregard for the safety of navigation of civil aircraft" when issuing regulations for their state aircraft. Contracting States also agree "not to use civil aviation for any purpose inconsistent with the aimsof [the] Convention." (85)
While the Chicago Convention did not adopt the liberal freedom of navigation regime for aircraft supported by the United States, (86) theConvention does permit the civil aircraft of contractingStates that are not engaged in scheduled flights to "make flights into" each others' territories and tomake stops for non-traffic purposes without the necessity of obtaining prior permission ..." subjectto a possible requirement for landing. (87) Statesmay regulate air traffic above their territories withoutdistinction based on nationality (with respect to other contracting States). (88) However, States maydesignate areas off-limits for reasons of military necessity or public safety, provided no distinctionis made between nationality of the aircraft. (89) Scheduled flight services may be operated over or intothe territory of a contracting State only with that State's permission and in accordance with the termsit may set. (90) Overflights using pilotless aircraftrequire special authorization. (91)
Nationality of Aircraft. Like ships on the seas, aircraft must be registered in one State only, (92) andmust bear the appropriate markings indicatingnationality and registrations. (93) Civil aircraft aresubject to regulation both by the State of registrationand, while flying over the territory of another State, that State's applicable regulations. Civil aircraftare also required to carry certain documents, including a certification of airworthiness, log book,radio license, a passenger list and a manifest of cargo. (94) No munitions or implements of war maybe carried as cargo over a State's territory without its permission. (95) States may make otherrestrictions with regard to cargo for reasons of public order and safety, provided the rules do notdiscriminate based on nationality.
State Aircraft. Under the Chicago Convention, the status of state aircraft is determined according to use rather than strictly by state ownership. (96) TheChicago Convention does not, however, enumerate rules governing state aircraft. Military aircraft,probably comprising the largest category of state aircraft, are treated much like warships. Militaryaircraft are defined under international law as those aircraft "operated by commissioned units of thearmed forces of a nation bearing the military markings of that nation, commanded by a member ofthe armed forces, and manned by a crew subject to regular armed forces discipline," (97) and are exemptfrom 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 actsperformed during official duties. Foreign officials may not board a state or military aircraft withoutthe consent of its commander, and in the event of a dispute regarding customs, immigration, orquarantine, the host nation is limited to requesting that the state aircraft leave the national territory. (99)
section_title: Enforcement Options
paragraphs: The following sections address the rights and obligations of States and non-public vessels andaircraft, which vary depending not only on location and status but according to whether the situationis considered one of war or peace, or somewhere in between. During peacetime, States generallyemploy 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 thehigh seas.
subsections: section_title: Law Enforcement in National Waters and Airspace
paragraphs: 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 isdoing. Maritime law enforcement measures may be taken when there are reasonable grounds forbelieving that a vessel is violating the validly applicable laws of the coastal State. (100) A coastal Statemay interdict ships suspected of engaging in illicit drug traffic, for example, without obtaining thepermission of the flag State, if the suspect vessel is located in the State's internal waters, archipelagicwaters, territorial sea, or, in some circumstances, its contiguous zone. (101) Warships of the coastalState are permitted to conduct hot pursuit of a foreign ship beyond the limits of its territorial sea orcontiguous zone if there is reason to believe the ship violated the applicable laws and regulations ofthat State and the pursuit is not interrupted. (102) The coastal State may not discriminate against shipsbased on their nationality or based on their cargoes to, from, or on behalf of any State. (103) The coastalState should not exercise criminal jurisdiction on board a foreign ship passing innocently throughits territorial sea for crimes committed on board the ship unless the consequences of the crime extendto the coastal State, the crime disturbs the "peace or good order," the flag State or the captain of thevessel requests assistance, or such measures are necessary to suppress the illicit traffic of drugs. (104)
section_title: Law Enforcement on the High Seas
paragraphs: 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 ambiguousnationality. However, UNCLOS and the Convention on the High Seas both identify certain activitiesas 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 thetransport of slaves in ships authorized to fly its flag and to prevent the unlawful use of its flags forthat purpose" (105) and to "co-operate to the fullestpossible extent in the repression of piracy on thehigh seas." (106) Piracy is defined as illegal actsof violence, detention, or depredation (plundering,robbing, or pillaging) for private ends in or over international waters. (107) Mutiny and hijacking donot amount to piracy unless the ship or aircraft seized is thereafter used to commit piratical acts. (108) Acts that would constitute piracy if committed for private ends are not piratical if committed forpolitical ends, for example, by insurgents not recognized as belligerents. (109)
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 tointernational conventions" and "co-operate in the suppression of unauthorized broadcasting from thehigh seas." (110) Neither convention addressesthe transport of weapons of mass destruction or ofmaterials useful in the production of such weapons.
Right of Approach and Visit. Merchant vessels, whether privately owned or State owned, may be stopped and boarded by the warships of non-flagStates under certain circumstances. The Convention on the High Seas specifies that a warship maystop and board a foreign merchant vessel if "there is reasonable ground for suspecting (a) [t]hat theship is engaged in piracy; or (b) [t]hat the ship is engaged in the slave trade; or (c) [t]hat, thoughflying a foreign flag or refusing to show its flag, the ship is, in reality, of the same nationality as thewarship." (111) UNCLOS reiterates thosejustifications and adds two more - (1) "the ship is engagedin unauthorized broadcasting ...," and (2) "the ship is without nationality." (112) With respect to thelatter 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 with respect to any other State, and may beassimilated to a ship without nationality." (113)
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 furtherexamination on board the ship, which must be carried out with all possible consideration." (114)
Enforcement Measures. With the exception of piracy and international broadcasting, however, neither convention specifies what actions a warshipmay take if the initial or further examination confirms the suspicions that justified the boarding inthe 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 bypiracy and under the control of pirates, and arrest the persons and seize the property onboard.
 (115)
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 thearea prior to entering. If circumstances do not allow such communication, the warship may be ableto enter the territorial waters of another state if necessary, but must depart immediately upon therequest of the coastal State. (116) A similar ruleapplies to piratical aircraft that flee into the nationalairspace of another State. 
With respect to a ship engaged in unauthorized international broadcasting, UNCLOS provides that a State having jurisdiction (117) "may ... arrestany person or ship engaged in unauthorizedbroadcasting 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 anyact justifying them, it shall be compensated for any loss or damage that may have been sustained." (119)
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 StatesCourt of Appeals for the Fifth Circuit held that the Convention on the High Seas conferred no rightswhatsoever on stateless vessels and upheld the seizure of an unregistered ship found by the CoastGuard 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 PITERfailed to do; her crew cannot complain of the results.
 (121)
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 flagState or further international agreement is necessary for a State to seize a ship flying the flag ofanother State, confiscate its cargo, or arrest and prosecute its officers and crew for engaging in otherprohibited activities. (122) Absent consent oragreement, the exercise of jurisdiction over the allegedlyunlawful activities of a merchant vessel appears to remain the prerogative and responsibility of theflag State. Weapons of mass destruction are not mentioned in UNCLOS or the Convention on theHigh Seas. It therefore appears that the visit, search, and possible seizure of ships on the high seasthat might be engaged in transporting weapons of mass destruction or materials useful in theproduction 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 informalarrangements that address the proliferation of weapons of mass destruction, (123) nor by the existingmultilateral conventions on terrorism. (124) Suchan authorization might well be negotiated on abilateral 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 ofvessels and aircraft on or over the high seas that are suspected of carrying WMD may only be validas a legitimate act of self defense or under a theory of "self-help," as described below.
section_title: The Proliferation Security Initiative
paragraphs: 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 "statementof interdiction principles" (see Appendix) committing member States to take action "consistent withnational legal authorities and relevant international law and frameworks, including the U.N. SecurityCouncil." (126) According to the PSI nations'statement, the initiative will target "States or non-stateactors 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 inproliferation through: (1) efforts to develop or acquire chemical, biological, or nuclear weapons andassociated delivery systems; or (2) transfers (either selling, receiving, or facilitating) of WMD, theirdelivery systems, or related materials. (127)
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 nonproliferationregimes. This statement may represent a reconsideration of the initial goal of the PSI; in announcingthe 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 missiletechnologies." (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, thePSI member States will allow ships flying their flags to be searched for WMD materials prohibitedby their laws where reasonable suspicion exists, and non-member States could be asked to consenton an ad hoc basis. However, it appears unlikely that States of proliferation concern, such as theDemocratic Republic of Korea or Iran, would consent to having their ships boarded and searched forWMD materials, and even if consent were obtained, there is no clear legal authority underinternational law, as it currently stands, for a State to seize WMD materials it finds on board, evenif 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 intoport. However, for a PSI State to stop and search a vessel traveling through its territorial sea couldimpede 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, orcontiguous 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 thatare identified,"and to "enforce conditions on vessels entering or leaving their ports, internal watersor territorial seas that are reasonably suspected of carrying such cargoes, such as requiring that suchvessels be subject to boarding, search, and seizure of such cargoes prior to entry." These activities,however, are to be conducted only "to the extent their national legal authorities permit and consistentwith 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 theflag-State, unless the vessels' passage is non-innocent. It is open to debate whether coastal nationshave the jurisdiction to prohibit the carrying of all WMD-related materials through their contiguouszones. (129) Non-participating States may objectto a requirement that their vessels submit to inspectionprior to entering the territorial seas of a coastal State as an effective suspension of the right ofinnocent 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 involvingthe use of force to deny aircraft passage or to enforce landings for inspections could raise objectionsfrom other nations. (130)
section_title: Belligerent Rights
paragraphs: 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, aneutral State maintains the basic rights of inviolable territory and the practice of commerce (unlessit involves providing contraband to the belligerents), but the neutral State must abstain fromparticipating in the conflict and maintain its impartiality as to the belligerents. Failure of a neutralship to act accordingly may result in a determination by a belligerent that the neutral has acquiredenemy character. Likewise, a belligerent must respect a neutral's inviolability and its entitlement totrade, 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 territoryis not being used by the belligerents in a manner inconsistent with its neutral status. In the event aneutral is unable or unwilling to police its territory for that purpose, a belligerent may take action toput an end to the misuse, even if such action requires the belligerent to enter the ordinarily inviolableterritorial sea of the neutral State. A neutral may prescribe conditions for belligerent warshipstransiting its territorial seas - or even prohibit their passage altogether - notwithstanding thecustomary right of innocent passage, as long as the regulations are applied impartially. A neutral isnot 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 forcontraband, to close the enemy's ports by means of a naval blockade, and of course, to use militaryforce against enemy warships and military aircraft. These belligerent rights, however, may beexercised only on the high seas or within the territorial seas of the belligerents, not withininternational 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 merchantships flying the flag of a neutral State and, if the ships are found to be carrying substantialcontraband of war to the enemy, to seize and condemn not only the contraband but the vessels aswell. (133) Goods deemed to be contraband undersuch circumstances clearly would include weaponsof mass destruction and goods useful in their development and production.
The right of visit and search does not extend into the territorial seas of neutral States or international straits overlapped by neutral territorial seas. (134) Neutral merchant ships are exempt ifthey 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 aresubject to search. (135)
Military aircraft also have the right of visit and search. (136) A military aircraft engaged in a visitand search mission would direct a suspected vessel to the vicinity of a friendly warship located onthe high seas or within the territorial waters of a belligerent State, allowing its crew to conduct thesearch, or it might direct the vessel to a belligerent port. (137) To visit and search another aircraft, themilitary 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 itsenemy's harbors with weapons or any other goods. The blockading State must declare the scope ofthe blockade and enforce it effectively and impartially. Once a blockade is declared, the ships ofneutral States with knowledge of its existence are bound to avoid the demarcated areas. Ships thatattempt to run the blockade are subject to capture and condemnation, along with their cargo. (138) Asan act of war carried out during an armed conflict between States, a blockade must be asserted inconformity 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 avisit and search, and are subject to capture if they are found to be carrying contraband or enemypersonnel, are operating under enemy control, orders, charter, employment, or direction; do notpresent valid documentation; or are violating regulations established by a belligerent within theimmediate area of naval operations; or are engaged in a breach of blockade. (139) Another variation onthe concept of a blockade of airspace is the "no fly zone," such as the restrictions imposed by theSecurity Council on aircraft flying over Bosnia and Herzegovina during the conflict there. (140)
section_title: Blurring the Boundary between War and Peace
paragraphs: 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 Chartercommits 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, whileat the same time maintaining that they are at peace. Consequently, the boundary between peace andwar has become blurred. Some commentators argue that a new paradigm is necessary to providerules necessary for the protection of States' interests in light of these changes in the character ofinternational conflict, the greater destructive power of modern weapons, and the emergence ofnon-state actors capable of mounting attacks against States. The following sections explore theuncertain 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 takeproportionate measures, including the use of force, that are necessary to protect itself from imminentharm. (141) Traditionally, that right included theuse of force to forestall an anticipated attack as wellas to respond to an attack. As Great Britain argued in the Caroline incident in 1837 (142) or, morerecently, as Israel contended in seizing a ship filled with arms bound for Palestine, that traditionalright could include not only the 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 specificallypreserves "the inherent right of individual or collective self-defence if an armed attack occurs againsta Member of the United Nations ...." (144) Scholars and publicists argue about whether Article 51affirms the traditional right of States to act in self-defense in its entirety or, as literally read, to allowit only after an armed attack has occurred. Yet even the more expansive reading still includes arequirement that an attack be imminent, and for some observers, the possession of WMD does notconstitute an armed attack. Others argue that the concept of imminence as applied to WMD mayrequire 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 (seeinfra). But more commonly the threat of an attack with such weapons - particularly if they are stillin the process of development - may be distant or inchoate. To the extent that is the case, thetraditional doctrine of self-defense may not provide firm support for the use of military means to stopmerchant vessels transporting weapons of mass destruction or goods useful in the development ofsuch weapons outside the context of an armed conflict. (145)
Pacific Blockade. An exception to the notion ofthe blockade as an act of war might be the so-called "pacific blockade." Distinguished from thebelligerent or wartime blockade, pacific blockade is not intended as a belligerent act and does notgive rise to a condition of belligerency unless the State against which the action is taken chooses toresist with force. A pacific blockade consists of naval action taken in peacetime to apply pressureagainst another nation by preventing the ships of the blockading and the blockaded nation fromentering or leaving specified areas of the latter's coast. The blockading State is only entitled to detainships, not to condemn or confiscate them or their cargo. All ships sequestered pursuant to a blockadeare to be restored to their owners when the pacific blockade is lifted. (147) Traditionally, the pacificblockade was effective only with respect to the vessels of the blockaded State; interference withvessels of a third State is generally considered impermissible, though practice has varied. (148)
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 anunlawful act on the part of the target State for the purpose of achieving reparations or otherwisesettling an international dispute. (149) Thelegitimacy of reprisals is said to depend on three conditions:that the purpose was to obtain remedy for injury resulting from illegal action, that non-coercivemethods to obtain such remedy had failed and that the measures taken were not out of proportion tothe 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 moveas an act of war, while allowing the United States to assert that the vessels of third States weresubject to the prohibitions. The United States did not assert the right to self defense under article51 of the U.N. Charter as a justification for its actions. (150) The strategy was successful in averting warat 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 ininternational law and it involves a distinctive situation, e.g., Cuba was viewed as a surrogate for itssupplier, the USSR. Some observers cite U.S. reaction to the Cuban Missile Crisis as an exampleof adapting international law to deal with new circumstances. (151)
Self-help Paradigm in International Law. Some theorists argue that the U.N. Charter may be construed to allow the use of proportionate force toprevent adversaries from producing, purchasing, or otherwise obtaining weapons of massdestruction. (152) Most scholars have interpretedArticle 2(4) of the U.N. Charter as a broad prohibitionon any use of force against another State, except where authorized by the Security Council actingunder its Chapter VII authority, or when the use of force is justified as necessary for self-defenseunder Article 51. (153) The alternate viewinterprets the U.N. Charter prohibition on the use of forcenarrowly to prohibit only certain kinds of armed attacks, namely, those "against the territorialintegrity or political independence of any State, or in any other manner inconsistent with thePurposes of the United Nations." (154) A surgicalstrike against a nuclear facility in a proliferant State,so the argument goes, would threaten neither the territorial integrity nor the political independenceof a target State, inasmuch as there would be no effort to annex or occupy territory, nor overthrowthe current political leadership. (155) Thelegitimacy of a preventive attack against WMD or theircomponents would rest on an interpretation of whether their destruction comports with the "purposeof 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 anotherwise unlawful attack might be justifiable. For example, Israel's 1981 aerial bombardment ofan Iraqi nuclear power facility, while condemned by the U.N. Security Council, (156) was viewed bysome as justifiable under international law and the U.N. Charter. (157) Others argue, however, that theU.N. Charter created the Security Council and entrusted collective security decisions primarily tothat body, leaving to member States the inherent right to defend themselves only in case of an armedattack. (158) According to that view, the role ofthe Security Council under the Charter and self-defenseprovision in article 51 seem to contradict a narrow interpretation of article 2(4) (159) that would alloweach State to decide for itself when a contemplated use of force is within the purpose of the UnitedNations.
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 compliancewith non-proliferation regimes cannot be counted on to rein in proliferant States and do not in anyevent apply to non-State actors bent on obtaining WMD. Proponents of this view urge the worldcommunity to adopt a paradigm shift that would revert to pre-U.N. concepts of internationalrelations, in which nations with sufficient strength were understood to have the power to takeself-help measures, including the use of force, to right international wrongs and enforce compliancewith international law. (160) Under this view,States would be justified in using preventive orpreemptive force to deter plans to acquire WMD, eliminate acquisition programs or destroy WMDcomponents or sites at any stage in the acquisition effort. (161)
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, (162) binding on all States whether or not they have agreed, by joining the relevant treaties, to desist fromdeveloping or acquiring WMD. (163) Under thisview, any State that persists in the development oracquisition of WMD, or permits its citizens and residents to do so with impunity, is committing awrongful act under international law for which other States may demand redress. Thus, althoughStates Parties retained the right to withdraw from the treaties upon giving notice, participation in thevarious non-prolifereration regimes, under this view, has become jus cogens - a mandatory andenforceable requirement of international law. (164)
There is some evidence that might support the argument that nonproliferation has become acustomary norm. (165) For example, the numberof States that have agreed to participate in thenonproliferation 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 astatement by the President of the U.N. Security Council in 1992 indicating that the Council considersproliferation of WMD to be a matter that poses a threat to international peace and security. (166) Withrespect 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 disarmament, armscontrol and non-proliferation, reaffirm the crucial contribution which progress in these areas canmake to the maintenance of international peace and security. They express their commitment to takeconcrete 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; toprevent the proliferation in all its aspects of all weapons of mass destruction; to avoid excessive anddestabilizing accumulations and transfers of arms; and to resolve peacefully in accordance with theCharter any problems concerning these matters threatening or disrupting the maintenance of regionaland global stability. They emphasize the importance of the early ratification and implementation bythe States concerned of all international and regional arms control arrangements, especially theSTART and CFE Treaties. 
The proliferation of all weapons of mass destruction constitutes a threat to international peace and security. The members of the Councilcommit themselves to working to prevent the spread of technology related to the research for orproduction 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 theintegral role in the implementation of that Treaty of fully effective IAEA safeguards, as well as theimportance of effective export controls. The members of the Council will take appropriate measuresin 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 thisconnection recognize the importance of all States providing all the information called for in theGeneral Assembly's resolution. 
(167)
The Bush Administration also points to positions taken by other international coalitions thatmay 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 Leadersannounced a new "G8 Global Partnership Against the Spread of Weapons and Materials of MassDestruction." (168) The European Unionpublished a set of principles June 10, 2003 for addressing theglobal 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 beenvisioned. The UN Security Council should play a centralrole. (169)
Finally, some suggest that the Proliferation Security Initiative may also serve as evidence of the progression of international law with regard to WMD, (170) although it remains to be seen what actionsit will entail and how other nations might react to its implementation.
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. SecurityCouncil excerpted above may be read as a promise to take action, but does not say what action theSecurity Council might take, and does not authorize States to enforce treaty commitments on the partof other States. It calls upon States to adhere to their treaty commitments and cooperate towardfurther international negotiations related to arms control. Moreover, as a statement rather than aformally 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 considerthemselves 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 nuclearweapons, since the relevant treaties prohibit all possession, trade, and use of such weapons bymember States, and require member States to adopt laws criminalizing the possession of bannedmaterials. Nuclear weapons, however, are not universally banned. (171) The NPT allows five Statesto stockpile nuclear weapons, and leaves it to their discretion as to whether possession on the partof their sub-national groups is criminalized under the national laws of member States. (172) Thisinconsistency appears to make the argument that the State possession of nuclear weapons is a juscogens violation less tenable. (173)
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 beprovided through alliance with one of the great powers, rather than evidence that States participateout of a sense of legal obligation. Part of the bargain, with respect to nuclear weapons, was that thefive nuclear powers negotiate to bring about an eventual total disarmament. (174) Now that the mutualdeterrence of the Cold War can no longer be said to be in operation, non-nuclear States may believetheir security requirements have increased, or that the strategic value of possessing nuclear weaponsoutweighs the benefit of remaining party to the NPT. (175)
Collective Action Under Security Council Mandate. Adherents of the "broad" interpretation of the U.N. Charter prohibitionagainst the use of force are more likely to view preemptive use of military force against WMDfacilities, including the interdiction of ships suspected of transporting elements of an unauthorizednuclear weapons program, to be legitimate only when the U.N. Security Council specificallyauthorizes it. (176) Under the U.N. Charter, theSecurity Council has "primary responsibility for themaintenance of international peace and security." (177) In this view, the Security Council is betterempowered to determine that WMD in the hands of only certain States and non-State actorsconstitutes 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 ofmember States. (178) It also has some options withrespect to enforcement. (179) Under its ChapterVIIauthority it could authorize a coalition of member States to organize and lead a force to carry outa 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 toSierra Leone. (180) In any case, nine "yes" votesfrom the U.N. Security Council are needed, with noneof the five permanent members exercising their veto.
section_title: Conclusion
paragraphs: International law recognizes that States have the right to interdict vessels and aircraft in certainlimited 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 proliferationconcern - at sea, in the air, and on land" (181) appears doubtful under the current state of internationallaw. The United States and its allies may consider whether to amend the treaties regarding the lawof the sea (and air) explicitly to include WMD and missile trade within the prohibitions that may beuniversally enforced. Other options include amending the proliferation treaties to enhancecompliance and, as the European Union stressed in its statement of non-proliferation principles, toreduce the perception among States that WMD are necessary for their own security. (182) Probably thefirmest legal basis for interdicting WMD materials would be provided by explicit authorization bythe U.N. Security Council.
section_title: Appendix A - Interdiction Principles for the Proliferation Security Initiative
paragraphs: PSI participants are committed to the following interdiction principles to establish a morecoordinated and effective basis through which to impede and stop shipments of WMD, deliverysystems, and related materials flowing to and from states and non-state actors of proliferationconcern, 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 internationalpeace and security to join in similarly committing to: 
Undertake effective measures, either alone or in concert with other states, for interdicting thetransfer or transport of WMD, their delivery systems, and related materials to and from statesand non-state actors of proliferation concern. "States or non-state actors of proliferationconcern" generally refers to those countries or entities that the PSI participants involvedestablish should be subject to interdiction activities because they are engaged in proliferationthrough: (1) efforts to develop or acquire chemical, biological, or nuclear weapons andassociated delivery systems; or (2) transfers (either selling, receiving, or facilitating) of WMD,their delivery systems, or related materials. Adopt streamlined procedures for rapid exchange of relevant information concerning suspectedproliferation activity, protecting the confidential character of classified information providedby other states as part of this initiative, dedicate appropriate resources and efforts to interdictionoperations and capabilities, and maximize coordination among participants in interdictionefforts. Review and work to strengthen their relevant national legal authorities where necessary toaccomplish these objectives, and work to strengthen when necessary relevant international lawand frameworks in appropriate ways to support these commitments. Take specific actions in support of interdiction efforts regarding cargoes of WMD, theirdelivery systems, or related materials, to the extent their national legal authorities permit andconsistent with their obligations under international law and frameworks, to include: 
Not to transport or assist in the transport of any such cargoes to or from states or non-stateactors of proliferation concern, and not to allow any persons subject to their jurisdictionto do so. At their own initiative, or at the request and good cause shown by another state, to takeaction to board and search any vessel flying their flag in their internal waters or territorialseas, or areas beyond the territorial seas of any other state, that is reasonably suspected oftransporting such cargoes to or from states or non-state actors of proliferation concern, andto seize such cargoes that are identified. To seriously consider providing consent under the appropriate circumstances to theboarding and searching of its own flag vessels by other states, and to the seizure of suchWMD-related cargoes in such vessels that may be identified by such states. To take appropriate actions to (1) stop and/or search in their internal waters, territorialseas, or contiguous zones (when declared) vessels that are reasonably suspected ofcarrying such cargoes to or from states or non-state actors of proliferation concern and toseize such cargoes that are identified; and (2) to enforce conditions on vessels entering orleaving their ports, internal waters or territorial seas that are reasonably suspected ofcarrying such cargoes, such as requiring that such vessels be subject to boarding, search,and seizure of such cargoes prior to entry. 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 ornon-state actors of proliferation concern and that are transiting their airspace to land forinspection and seize any such cargoes that are identified; and/or (b) deny aircraftreasonably suspected of carrying such cargoes transit rights through their airspace inadvance of such flights. If their ports, airfields, or other facilities are used as transshipment points for shipment ofsuch cargoes to or from states or non-state actors of proliferation concern, to inspectvessels, aircraft, or other modes of transport reasonably suspected of carrying suchcargoes, and to seize such cargoes that are identified.
Source: White House Fact Sheet, Sep. 4, 2003, available at http://www.whitehouse.gov/news/releases/2003/09/20030904-11.html .