On june 17, 2009, an American destroyer began following the Kang Nam, a North Korean ship suspected of carrying missile components to Myanmar. As the New York Times headline read, “Test Looms as U.S. Tracks North Korean Ship.” Despite United Nations Resolution 1874, adopted five days earlier, which called “on Member States to inspect and destroy all banned cargo [traveling] to and from” North Korea, the U.S. did not stop or board the ship.

In December 2002 the Spanish Navy intercepted a ship carrying scud missiles capable of being armed with nuclear warheads traveling from North Korea to Yemen, a known terrorist haven. When warning shots were fired across the So San’s bow without response, Spanish special forces boarded the ship from a helicopter using fast ropes. Spain discovered the missiles, which were not on the ship’s manifest, hidden by 40,000 bags of cement. Yemen claimed the shipment was for legitimate defensive purposes, but the steps that had been taken to conceal the missiles, North Korea’s involvement, and Yemen’s terrorist links gave the world reason to worry. The So San was allowed to continue to its destination with its missiles.

Since beginning to monitor incidents of nuclear trafficking in 1995, the International Atomic Energy Agency (iaea) has documented at least 196 instances of illegal trafficking, including at least 18 that involved weapons-grade, highly enriched uranium and plutonium, the primary fuel of nuclear weapons. Given these statistics, one might have expected international law to become much less hospitable to nuclear traffickers after terrorists made their intentions clear on September 11. Yet the nonproliferation regime in some ways looks very much like it did before the towers fell, providing surprisingly little room to combat the spread of nuclear weapons.

If this sounds counterintuitive, it is for good reason. The un has often made pronouncements denouncing proliferation, including Resolution 1874 five days before the Kang Nam incident and Resolution 1540 in 2004, declaring that nuclear proliferation “constitutes a threat to international peace and security.” However when it comes to a crucially important component of nonproliferation — physically stopping the transport of prohibited material — international law generally precludes action in international waters. The U.S. and Spain understood this, which explains the treatment of the North Korean ships.

This essay will argue that international efforts to date do not go far enough in preventing proliferation by sea. It will examine the current state of interdiction policy; provide historical and forward-looking justifications for change; explore why change has not occurred; and, finally, advocate a politically realistic path for reform.

The state of interdiction policy

The united nations Convention on the Law of the Sea (unclos) is the primary treaty governing the oceans. It gives every state control of the seas extending twelve miles from its coast, and the water beyond this is considered the “high seas,” or international water.1  The treaty establishes what is known as flag-state sovereignty. This means that only a state whose flag a ship is flying can interdict that ship in international water. The law of the sea treats a ship on the high seas as if it were part of a state’s physical territory, a sort of floating embassy.

unclos does include a limited number of conditions under which one state may board another’s vessel without consent, but these exceptions exist only if the ship is reasonably believed to be engaging in piracy, slave-trading, or unauthorized broadcasting. There is no exception for nonproliferation purposes, despite its posing a greater danger to the world today. If there is clear evidence that a nuclear weapon is onboard a ship and will be imminently used in an attack, then a claim of self-defense, under Article 51 of the un Charter, can be used to justify intercepting the ship. But if a North Korean ship is simply carrying weapons-grade uranium on its way to Syria, there is little the international community can do to stop it without North Korea’s permission. A claim of preemptive self-defense would likely be seen as too far-reaching, given that the uranium would not pose an immediate threat to another country’s security.

The Proliferation Security Initiative was launched by the Bush administration in 2003, partly in response to the So San incident.

Against this backdrop, consider some of the international community’s more prominent efforts to combat proliferation since September 11. The Proliferation Security Initiative was launched by the Bush administration in 2003 partly in response to the So San incident. psi is a voluntary organization in which countries agree to take steps to halt proliferation, including facilitating interdiction at sea. The psi was highly publicized by the Bush administration in the wake of September 11 as a crucial multilateral effort. psi has been highlighted in at least ten speeches by senior State Department officials since its launch in 2003. And it is clearly a worthwhile endeavor, having led to at least 11 interdictions. But what is crucial to understand is that psi does not change unclos’s principle of flag-state sovereignty. A psi participant can agree to grant permission to other countries to board its ships in international water. Or, countries can sign separate bilateral ship-boarding agreements granting each other the right to board one another’s ships, as the U.S. has done with popular ship registries such as Bahamas, Belize, Croatia, Cyprus, Liberia, Malta, the Marshall Islands, Mongolia, and Panama. But neither the psi nor the ship-boarding agreements that have followed it allow any action that violates unclos’s dictate of flag-state sovereignty. As John Bolton made clear in a 2003 speech shortly after the launch of the psi, “Actions taken under the psi will be fully consistent with national legal authorities and relevant international law and frameworks.” This means that if North Korea (which has not joined psi) wants to transport nuclear material, all it has to do is to use a North Korean flagged ship rather than a ship of a psi signatory.

Similarly, consider the prominent un nonproliferation efforts, Resolutions 1874 (2009) and 1540 (2005). The former denounces North Korean nuclear tests and demands cessation of nuclear activities in sharp language: “The dprk shall abandon all nuclear weapons and existing nuclear programmes in a complete, verifiable and irreversible manner and immediately cease all related activities.” However, the resolution provides little real authority for the international community to follow this talk with action. The resolution simply “calls upon all Member States to inspect vessels, with the consent of the flag State, on the high seas, if they have information that provides reasonable grounds” to believe the ship is engaged in proliferation (italics added). The resolution is carefully worded not to change the principle of flag-state sovereignty. In the same manner the preamble of resolution 1540 highlights that un members are “gravely concerned by the threat of terrorism . . . [and] by the threat of illicit trafficking in nuclear, chemical and biological weapons.” But the resolution ultimately just “calls upon all States, in accordance with their national legal authorities and legislation and consistent with international law, to take cooperative action to prevent illicit trafficking in nuclear” weapons (italics added). Again, the resolution’s words are carefully chosen to bow to the existing framework of flag-state sovereignty. All a proliferator has to do to avoid these resolutions is to transport cargo on its own ships or on the ship of another country that will not allow inspection on the high seas.

While psi and the un resolutions are worthwhile in that they make fewer avenues available to proliferators, they thus do not fundamentally solve the problem underlying the Kang Nam, So San, and other incidents, which is an inability to act in international waters without consent. In this sense, post-September 11 efforts might be accused of preaching to the choir: Those who sign un resolutions, join psi, and consent to inspection of their ships are those already committed to nonproliferation. But it is the countries that remain outside these agreements that are the most likely proliferators. International law does not match international rhetoric, doing little to restrain the countries that matter most.2

A historical justification for change

The current state of affairs is that despite grand international resolutions, ships carrying nuclear material cannot be interdicted in international water. Yet it is too easy to rush to the conclusion that something must change, that the war on terrorism demands the ability to interdict on the high seas. Flag-state sovereignty is an old and cherished principle, so it is important to carefully consider what might be lost by amending it.

The notion that the seas are free for all nations to navigate can be traced as far back as the Roman Empire in the West and at least equally as far back in Asia. But the principle largely vanished after Rome’s fall in the fifth century until reemerging in the early 17th century in the voice of Hugo Grotius, a Dutch jurist. Grotius wrote to defend his country’s right to use trade routes to India and the East Indies, over which Spain and Portugal claimed a monopoly. The first paragraph of his now famous Mare Liberum states that “Every nation is free to travel to every other nation, and to trade with it.”

Grotius’s ideas, however, did not take hold for nearly 200 years. Until the Industrial Revolution, European countries continued to exercise control over as much of the oceans as their power allowed. But with the Industrial Revolution came the increasing importance of commerce, and thinkers such as David Ricardo emphasized the gains from free trade that would come to all nations. Thus, led by Great Britain and its navy, Grotius was resurrected. Freedom of the seas became part of customary international law until it was finally codified in the un-led 1958 Convention on the High Seas, from which unclos, its successor and the law today, borrows language almost exactly.

Since PSI’s launch, only a handful of interdictions a year have become part of the public record.

This brief historical context reveals that commerce has been a key reason for flag-state sovereignty’s emergence; it is therefore important to consider whether commerce will be damaged by nonproliferation goals. The numbers are easy. Since psi’s launch, only a handful of interdictions a year have become part of the public record. This is minuscule compared to the hundreds of thousands of ship voyages that occur annually. It thus seems reasonable that interdiction would hardly cause trade to suffer. Yet even if trade were noticeably damaged, the argument for amending flag-state sovereignty could still hold. It would be a matter of weighing the lost trade against the benefit from better curbing proliferation. Over the past few centuries, as flag state sovereignty ingrained itself in international law, the prospect of nuclear terrorism did not exist as it does today. There is therefore no reason to assume that the optimal balance between trade and security was achieved historically, and it would be appropriate to re-strike this balance.

Of historical significance, such a re-striking occurred in the debate over flag-state sovereignty and the slave trade. The 1958 Convention on the High Seas represented the first time that nations were given the right to board the ships of other states if these ships were suspected of carrying slaves. This provision was hotly contested before it was adopted because of the exalted status of flag-state sovereignty. In fact, in a 1956 United Nations conference on slavery, a proposal to allow the boarding of ships without sovereign permission was defeated. Yet two years later this right was granted, and Myres Smith McDougal and William T. Burke, two noted international lawyers of the time, wrote in its defense:

It seems reasonable to assume that the potential adverse impact of permitting visit and search of merchant vessels by foreign warships for this limited purpose [prohibiting slave-trading] would not reach any significant proportions in interference with lawful transport. The human misery and suffering to be avoided by recognition of the limited authority involved in the right of visit and search for this purpose seems, on the other hand, of sufficient importance to warrant the slight risk that some states might abuse the authority granted and interfere with transportation of a legitimate kind.

Much the same logic about the minimal impact to legitimate transportation and the potential to avoid human suffering applies to interdiction to prevent nuclear proliferation.

A forward-looking justification
for change

A less analytical but intuitively powerful reason for amending flag-state sovereignty is found not by weighing historical costs and benefits but by considering what the world might look like if a terrorist nuclear attack succeeds. If for instance the U.S. were attacked, the country would have the moral imperative and political will to prevent another detonation by stopping future nuclear shipments. Additionally, the sympathy of the world would be so aroused that U.S. action would likely have broad international support.

It thus seems probable that interdicting for nonproliferation purposes would come to be accepted after a terrorist nuclear attack. It should therefore be permitted before one. There is little logic in arguing that a nuclear explosion, with its accompanying loss of life and threat to peace, must occur before interdiction is allowed. As with the historical argument based on trade, this forward-looking claim does not maintain that high seas interdiction is currently permitted, only that it ought to be. The remaining question is how to bridge the gap between the “is” and the “ought.”

In asking how change might be brought about, it is helpful to first ask why change has not yet occurred. One possibility is that international law does not easily adapt to new political realities. Domestic law has a well-identified means of change. If a law is not serving its needed purpose, a legislative body can typically amend the law by majority vote. But international treaties are extremely difficult to amend. Treaties allow participants to withdraw, but changing the terms of a treaty usually requires unanimous consent of the signatories (the Vienna Convention on the Law of Treaties establishes that treaty amendments can only bind countries that agree to them). Since some states, most notably North Korea and Iran, actively flout the nonproliferation regime, they would almost certainly not participate in any treaty allowing interdiction, and as with psi, the states of greatest concern would be outside the system.

While (or perhaps because) treaties are difficult to amend, change in international law has often been brought about by unilateral action. International law is replete with examples of one state breaking with custom in order to establish a new practice, and other states either embracing this new practice and thereby making it new customary law or rejecting the practice and trying to restore the previous order. In fact, several extremely important laws in the maritime regime came into being in precisely this way. For instance, in 1945 President Truman unilaterally declared in what became known as the “Truman Proclamation” that the U.S. would have exclusive use of its continental shelf. After Truman’s declaration, so many other states followed suit that the idea that coastal states have a claim on the continental shelf was incorporated into the 1958 Convention on the Continental Shelf. As a 1969 International Court of Justice (icj) ruling described history:

The Truman Proclamation . . . soon came to be regarded as the starting point of the positive law on the subject, and the chief doctrine it enunciated, namely that of the coastal State as having an original, natural and exclusive right to the continental shelf off its shores, came to prevail over all others.

Similarly, in 1951 Norway changed international law through unilateral action. It seized a British trawler off of the Norwegian coast, claiming that the ship was in Norwegian waters. This claim depended on a new definition of Norwegian waters. Norway possesses thousands of small islands off the coast of its mainland. Under then-existing international law, the water between the mainland and islands did not belong to Norway. Yet Oslo made a new argument that its coast was defined by an imaginary line connecting its islands, rendering the water in question internal water, much like a landlocked lake. This practice of defining a coastline by a country’s outer islands was subsequently deemed acceptable in an icj decision and led to a number of other countries adopting similar practices. In fact, the practice became so widespread that it was permitted by treaty in 1958 and remains in unclos today. As was the case with the continental shelf, unilateral action created new international law.

If international law, though rigid, can be changed by unilateral action, why have the U.S. or other countries not interdicted nuclear material on the high seas in order to redraw the boundary of permissible action? The simple answer is fear of retaliation by the country whose ship is boarded. While the U.S. claim to its continental shelf and the Norwegian claim to a new coastline appropriated territory which had previously belonged to mankind, a nonconsensual interdiction on the high seas would be a direct affront to a specific country. Wars have been fought over similar acts. The risk of escalation of an individual interdiction into war is a serious one, and must factor heavily into the calculus of decision-makers. Indeed, it is only by addressing this risk that interdiction policy can change.

A new approach to change

To date, the international community has tiptoed around flag-state sovereignty. The Kang Nam and So San were identified as worrisome but allowed to continue. The U.S. launched psi but has been careful to state that it does not permit nonconsensual boarding. un resolutions denounce proliferation but use language carefully chosen to avoid calling for interdiction. Yet at some point, if the international community is committed to nonproliferation, the line that has so far been avoided is going to have to be crossed and a ship on the high seas will have to be stopped without consent. In order to avoid an escalation of this incident, the international community must first lay the proper foundation.

A promising approach to establishing this foundation is found outside of international relations literature, in examples for how to bring about change in domestic law. In a paper called “Gentle Nudges vs. Hard Shoves: Solving the Sticky Norms Problem,” Dan Kahan, a professor at Yale Law School, argues that incremental approaches to change are more effective than abrupt ones. In his words, “norms stick when lawmakers try to change them with ‘hard shoves’ but yield when lawmakers apply ‘gentle nudges.’” 3 The underlying intuition is that if lawmakers change laws quickly, society is too wedded to old norms to change behavior. But if laws adapt gradually, society buys into the change. For example, starting in the 1960s Congress took its first steps against tobacco, requiring warning labels. Six years later it banned television advertisements. Lawmakers then restricted smoking in public places, and eventually society’s attitudes towards smoking had so evolved that smoking became widely banned in private establishments like restaurants. Had lawmakers attempted to impose today’s regulations in the 1960s there would have been a backlash. And in fact there was a backlash in the European states that took a less gradual approach than the U.S. to tobacco regulation.

Similarly, narcotics regulation began very incrementally. Early in the 20th century opium, cocaine, and marijuana were legal and common. Starting in 1914 there was gradual regulation over who could dispense these drugs, and over time this developed into the strict drug laws in place today. This model of successfully banning narcotics is very different from the history of alcohol regulation. While Prohibition failed for many reasons, one was that it was such a sudden change from the past, so society had difficulty accepting what its legislators had decreed.

This notion of incrementalism can be applied to nonproliferation, and there are several small steps countries can take before the first interdiction. First, those states committed to nonproliferation can enter into a multilateral agreement allowing any member of the group to board another member’s ship if suspected of illegal proliferation. This would be a significant step beyond the Proliferation Security Initiative, since the psi simply encourages countries to cooperate on interdiction efforts and stops short of allowing boarding without permission. While proliferators would not be willing to sign an agreement authorizing interdiction, the existence of a multilateral pact among like-minded states would plant the principle of interdiction firmly in the soil of international law. A group of countries giving up sovereignty for nonproliferation would cross a line that has not been crossed in a multilateral treaty before, rendering the line less firm. Further, this is not something which should be overly difficult for most nonproliferation focused states, given that many have already abandoned flag-state sovereignty for piracy and the slave trade.

A second “gentle nudge” like-minded states could take would be to establish a system of liability in case a ship is wrongly stopped.

A second “gentle nudge” like-minded states could take would be to establish a system of liability in case a ship is wrongly stopped. The idea would be to legitimize the notion of interdiction by providing restitution if interdiction is abused; for if the notion of restitution for incorrect use of a power is accepted, then the idea that this power can be correctly used is implicitly endorsed. Establishing a system of liability would also allow interdicting countries to claim moral authority much more strongly. It would undermine a claim that interdiction is just the strong having their way with the weak without consequences. Further, it would help to assuage the pride of countries whose ships are stopped. If targeted states know that they will be compensated for faulty interdictions, some of the sting of interdictions will be removed and retaliation will be less likely. Notably, unclos establishes that if one state seizes another state’s ship on the high seas out of suspicion of piracy, and this seizure occurs without “adequate grounds,” then the seizing state is liable to the flag-state for any loss or damage. A similar approach of just compensation for faulty interdictions could work well for the nonproliferation regime.

Once the notion of interdiction has been accepted by the vast majority of states that are concerned with nonproliferation, and once a system of liability has been established, a further gentle nudge will be needed to cross the final line and board a ship of a noncooperating nation without consent. This is the point at which retaliation is the greatest concern, and so the first interdiction should be one for which there is especially strong evidence that the cargo will be used for illicit nuclear purposes. Some ships will carry material that is ambiguous, either because it has dual-use capability or its destination is uncertain. The So San and the Kang Nam were in this category, based on information made public. Conversely, the first interdiction should involve a ship carrying cargo for which there is compelling intelligence that weapons will be used by terrorists. Such cargo is so obviously for evil purposes that morality would clearly be on the side of the interdicting state. The legitimacy of any retaliation would therefore be severely undermined in the eyes of the world, facilitating broad international support for the interdiction and reducing the likelihood of escalation.

This strategy of incrementally chipping at the flag-state sovereignty line will require patience. Nonproliferation advocates will have to be pickier than some would advocate in selecting target ships, especially early on. Because of the dynamic by which international law changes, the first nonconsensual boarding is most likely to cause retaliation, as various powers seek to ensure the international system either embraces or rejects interdiction as an appropriate action. If the first interdiction succeeds, then the second one becomes slightly easier. The third in turn again encounters marginally less opposition, and nuclear interdiction can in this manner slowly work its way into the fabric of international law, ultimately allowing cargos such as those on the Kang Nam and So San to be stopped. The path to change will be slow, but the virtue of a patient approach is that it takes seriously the consequences of retaliation. A patient course is better than one which escalates into war. And it is better than the status quo — a world in which less can be done to stop nuclear trafficking than piracy or the slave trade, and in which interdiction policy has changed little despite the emergence of nuclear terrorism and the threat it poses to our way of life.

1unclos Article 3 addresses the 12 mile territorial sea limit. Article 57 also grants to states limited economic rights up to 200 nautical miles from their coast. Many commentators argue that since this Exclusive Economic Zone covers economic rights, it is legally equivalent to the area seaward of it for interdiction purposes. A minority argue that interdiction rights are different in the eez than in the area seaward of it.

2 Another international accord that implicates the high seas but does not have direct import to this discussion is the Convention for the Suppression of Unlawful Acts Against the Safety of Maritime Navigation (sua). sua seeks to ensure that “appropriate judicial action is taken against persons committing unlawful actions against ships” and the 2005 Draft Protocol extends sua to cover the transport of wmd for terrorist purposes.

3 Dan M. Kahan, “Gentle Nudges vs. Hard Shoves: Solving the Sticky Norms Problem,” University of Chicago Law Review 67 (2000).

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