Earlier today, Blake wrestled with the question of whether an attack on Iran would be legal under United States law. But what about under international law? After all, the vagaries of the War Powers Act and Congressional resolutions are a sideshow from the perspective of international lawyers. What really matters is whether a U.S. attack would violate the U.N. Charter's prohibition on the use of force. There are two main roads around that prohibition: the U.N. Security Council and a claim of self-defense (Article 51 of the Charter preserves the "inherent right" of self-defense).
The Security Council, of course, can bestow legality on just about whatever it pleases. If it says that Iran's nuclear program is a threat to international peace and authorizes force, the bombs can lawfully fall. But in today's political climate, that prospect appears remote. China, Russia, and France show no signs of being ready to authorize force, and they have carefully steered existing resolutions away from that dangerous ground. Unlike with Iraq, there's no web of pre-existing Security Council resolutions authorizing force against Iran. Remember: Creative State Department and British Foreign Office lawyers argued that the current Iraq war was lawful because Iraq never complied with the Council's demands on disarmament, thus activating the previous authorization of force. (I always thought it was a strained argument, but at least it was—in lawyer's parlance—"colorable.")
That leaves self-defense. The use and abuse of the legitimate doctrine of preemptive self-defense has been well documented. In light of Iraq, the United States would have a very hard time making such a claim stick. But Israel, interestingly, has a stronger case (what with Iran's military support for Hezbollah and the threats to wipe Israel off the face of the map). Could the United States legitimately piggyback on Israel's claim to preemptive self defense—making it collective preemptive self defense? I'm going to do some digging on what legal scholars think about that question and will report back.