Is It Legal For the U.S. To Use Force Against Iran?

Ideally, any military strike against Iran would also be authorized by the United Nations. But a Security Council resolution is likely to be vetoed by Russia and China. To act unilaterally, the United States would have to argue that an attack on Iran was justified as an act of anticipatory self-defense because the threat of a nuclear-armed Iran is so great that we cannot wait until an attack is imminent. But in the absence of U.N. authorization, many nations, including some of our allies, are likely to believe that a preemptive attack would violate international law, just as they believed the U.S. invasion of Iraq violated international law (despite the prior Security Council resolutions). The president could reasonably argue that he has constitutional authority to use force without congressional authorization because a nuclear-armed Iran is a real threat to the United States. But he would be on stronger legal and political ground if he first sought legislative approval. While many members of Congress might not object if the president were to proceed unilaterally, the Constitution gives Congress the responsibility “to declare war.” Congressional approval is important. A military strike on Iranian nuclear facilities might require multiple sorties over several days and would surely be regarded by Iran as an act of war. Like all military actions, the outcome is not certain and where it leads is not within our control. Congress should hold hearings to consider the implications of an attack — which include possibly provoking terrorist attacks against the United States, a wider regional war and damaging the U.S. economy — as well as the resulting costs and how to pay for them. An explicit congressional mandate authorizing the use of force unless Iran meets specified requirements would demonstrate to all our resolve to prevent Tehran from developing nuclear weapons. The threat posed by Iran’s aggressive pursuit of a nuclear weapon is grave. Obama and Romney are right to say that the United States is prepared to use force to defend the nation against this threat, if that is necessary after other means have been exhausted. But both men should also explain a clear legal basis for a military strike. They should publicly commit to seeking specific congressional authorization to bolster the president’s constitutional authority to defend the United States. And they should explain how using force against Iran would be justified under international law and under what circumstances.