For more than a week now, U.S. warships have been tailing a North Korean vessel suspected of carrying illegal weapons while it sails round in circles off the coast of China. The latest U.N. Security Council resolution on North Korea (RES. 1874) has proved to be nothing to laugh at, and may well have led Burma--the ship's supposed destination--to revoke its invitation for a North Korean port call. That, in turn, may soon compel Pyongyang to bring the vessel back to home port.

Resolution 1874 allows our navy to board North Korean ships, but only if North Korea agrees, which is not very likely. A ship, though, in effect consents to inspection when it requests permission to dock in a foreign port, and the resolution directs host countries to inspect any vessels suspected of carrying illegal North Korean weapons and to deny them fuel and water until the grounds for suspicion are dispelled. That is new, and it could well have created a serious problem for North Korea. After many days heading south, the vessel is now--very slowly--heading back north again, and may soon run out of fuel. So far, so good.

What's not so good is the ubiquity, in reports and official statements, of arguably the most unfortunate word in the lexicon of American diplomacy: "authorization." In order to secure support for the resolution, Susan Rice, the new U.S. ambassador to the United Nations, agreed that it would not "authorize the use of force" to interdict any suspect North Korean vessel. The implication is that without the Security Council's authorization, forcible interdiction would be illegal.

If you don't see how that can be a problem, just remember what happened in 2003 when we promised Tony Blair that we would seek a "second resolution authorizing force" against Iraq and then followed him straight into an ambush in the Security Council. It hardly mattered that according to the State Department, force was already authorized and a second resolution would only be icing on the cake. We agreed to seek authorization, failed to get it, and then invaded anyway. It was a diplomatic disaster, with strategic consequences that are still being felt.

The United States does have good reason to hesitate before interfering with foreign ships on the high seas. In the earliest years of the American nation, vindicating "freedom of the seas" was the highest priority of our foreign policy, considered even more pressing than the final definition of our borders. Now, as we are trying to make it as difficult as possible for North Korea to navigate freely in the "global commons," international compliance with the sanctions regime could fall apart if the United States is not the first to uphold the freedom of the seas.

But that does not mean we should give up the rights we actually have, especially not that of self-defense.

Consider the Cuban Missile Crisis. When it was discovered that the Soviets were setting up nuclear missiles in Cuba, President Kennedy ordered a "quarantine" of the island, requiring all ships sailing in waters around Cuba to submit to U.S. naval inspection or leave the area. Kennedy's threat to use force against Soviet warships violating the quarantine was probably the closest the world ever came to nuclear war.

But such a naval blockade had not been "authorized" by the Security Council. The American Journal of International Law published a commentary at the time ("on behalf of the board of editors") arguing that the quarantine was contrary to international law as it had not been "authorized" by the Security Council. Kennedy would have none of it. "We, of course, keep to ourselves and hold to ourselves," he said at a press conference, "under the United States Constitution, and under the laws of international law, the right to defend our security."

The U.N. Charter was adopted at the San Francisco Conference of 1945, in which the 50 victors of World War II took up a draft treaty devised mainly by the Russians, British, and Americans the year before. As proposed in that draft, the key prohibition on the use of force required states to "refrain in their international relations from the threat or use of force . . . in any manner inconsistent with the Purposes of the United Nations"--purposes which included "the prevention and removal of threats to the peace."

But at the conference, a poorly worded amendment to the prohibition opened the door for future generations of international law scholars to argue that any use of force not specifically sanctioned by the charter would require Security Council authorization. In the form finally adopted as Article 2(4) of the charter, member states agreed "to refrain from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations" (our italics tracking the changes). If one thinks any exercise of force threatens the "political independence" of the state at which it is directed, one might read this as a complete prohibition on any and all uses of force--as some commentators have argued ever since. The charter would blur the distinction between legitimate and illegitimate uses of force.

After the new wording was accepted, certain conference delegates insisted on a new clause to make clear that states would still have a right of self-defense. Other delegates objected that this was pointless and silly, that self-defense was an inherent right which could not be impaired by treaty, and that a clarification could do more harm than good. What emerged from the confusion over Article 2(4) was the incoherent Article 51, which enshrines "the inherent right" of self-defense, but only "if an armed attack occurs." There is a lot of disagreement about the meaning of Article 51, but everyone seems to agree that it cannot mean what it actually says. Even Kofi Annan reads into Article 51 the right to preempt an "imminent" attack.

The wording of the charter has made the right of self-defense a rich subject for legal scholars. In the real world, however, the pattern of state practice since 1945 suggests that the inherent right of self-defense remains what it always was: Self-defense is justified when it is necessary and when the action taken is proportional to the need. The blockade of Cuba during the Missile Crisis, like the subsequent U.S. military interventions in Grenada, Panama, and Serbia, were all actions taken without Security Council authorization, on the basis of legal positions that boiled down to necessity and proportionality. In his 2008 AIPAC speech, even Senator Obama unequivocally endorsed Israel's 2007 strike on a nascent Syrian nuclear reactor, an act of preemptive self-defense where no attack was "imminent," but which was clearly both necessary and proportional.

Under the terms of the U.N. Charter, the Security Council can command and can prohibit, and its pronouncements must be obeyed. But the charter does not assign responsibility to the council to "authorize" states to do things. Is it really plausible that Churchill, Stalin, and Truman meant to commit their nations to passivity in the face of serious threats until they had permission from the Security Council to act against them? Is it plausible to think that Russia or China would seek permission--and subject itself to our considered or ill-considered judgment on its proposed actions--in matters it judged vital to its own security? It would be a fantasy to think so. Saddam Hussein had a similar fantasy in 2003--imagining that French actions at the United Nations could save him. It can't be good for anyone to encourage similar fantasies in Pyongyang today.

The Security Council is valuable chiefly as a tool for building political coalitions. When North Korea invaded the South in 1950, the council "recommended" that states come to its defense and that they put their forces under U.S. command. It "authorized" those forces to fly the U.N. flag. It didn't "authorize" anyone to use force because no "authorization" was needed: The defense of South Korea was indisputably legal even according to the most outlandishly restrictive interpretation of Article 51.

The first time that the council actually "authorized" the use of force was with Resolution 678--the Gulf War resolution of 1990--in which it "authorized" all necessary means to expel Saddam from Kuwait. The defense of Kuwait was every bit as legal as the defense of South Korea 40 years earlier. The George H.W. Bush administration needed the resolution not for legal reasons, but for purely political ones--it needed Congress and the Russians to be on board, and the council resolution was both cover and cudgel.

The administration chose "authorize" as a weaker version of "recommend" or "call upon" without meaning to imply that the United States needed any resolution under international law. Yet only 12 years later, some of our own allies claimed that we needed Security Council authorization in order to enforce the original Gulf war resolutions. If the council had just "recommended" or even "called upon" states to help liberate Kuwait, the resolution would have served its political purpose without any adverse implications under international law. But the precedent was set, and so were the terms of many future debates about our diplomacy.

What if we had evidence that a North Korean ship might be carrying nuclear materials to Iran? It is difficult to believe that Obama would wait on council authorization in a situation that clearly demanded immediate action. The Obama administration contains its share of hawks and has given clear signs that all options remain on the table for the defense of our vital interests. But if he's smart President Obama will also leave plenty of room between the rights he claims and the decisions he eventually takes.

It may not be prudent to board North Korean vessels right now, but it is dangerous to give the impression that we don't have the right to do so. It's dangerous because it erects an unreasonable standard of "lawful" conduct which we may well have to violate another day and because it encourages states like North Korea to think that they can do as they please on the high seas.

North Korea has already inflicted enormous damage on the nonproliferation regime; the cancer of nuclear proliferation among rogue regimes has already begun to metastasize because of North Korea's nuclear breakout after 1994. Coming from a criminal regime, which has declared itself to be once again at war with the United States, the illegal weapons or nuclear materials aboard any of those vessels could constitute a proliferation risk of such gravity as to make a forcible inspection of the contents both necessary and proportional.

When the intrinsic legality of an action taken in self-defense is manifest, its legitimacy cannot depend on political endorsement from the Security Council. Those who suggest otherwise are advocating not for international law, but for world government. The job of the U.S. mission to the United Nations is to vindicate the sovereign rights of the United States, not transfer them to an undemocratic and unaccountable international organization. The Security Council needs to get out of the business of authorizing us to do things that we already have the right to do.

Jeremy Rabkin is a professor of law at George Mason University and the author of Law Without Nations? Mario Loyola, a fellow at the Foundation for the Defense of Democracies, is a former adviser in the U.S. Senate and at the Pentagon.

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