We are having this conversation now because of the April 7 strikes on the Shayrat Airfield in Syria, but the question of how one justifies forcible measures in the context of a humanitarian emergency, and in the face of a deadlocked Security Council, is one that deserves urgent attention beyond the context of any single event. Progress toward answering this question has, however, been mired in a long-standing debate between those who believe that there is no credible international law justification for humanitarian intervention—and that the U.S. government should instead justify interventions like those taken at Kosovo and Shayrat as morally “legitimate”—and those who believe a legal justification can and should be put forward. I am very much in the latter camp and will use my time now to explain how I arrived at this position as a policy and as a legal matter by looking at three questions: the first question is whether legal justification is the direction that the United States should go in as a matter of policy. The second question is whether legal justification is credibly available as a matter of international law. The third question (which assumes the answer to the first and second is yes) is how to go about articulating and disseminating such a justification. Let me take these in order.