Is the current international legal regime capable of deterring and stopping mass atrocities? Recent events in Darfur again raise this familiar question of whether international law facilitates the kind of early, decisive, and coherent action —especially with respect to military force —needed to combat genocide effectively. In this report, Matthew C. Waxman argues that an international legal regime that puts decisions about international intervention solely in the hands of the UN Security Council risks undermining the threat or use of intervention when it may be most potent in stopping mass atrocities. The features of the UN Charter that help resolve security crises peacefully make it difficult to generate the rapid action needed to deter or roll them back. Waxman urges the United States and other Security Council members to take steps to improve the responsiveness of the existing Security Council. He insists that they signal the willingness, if the UN fails to act in future mass atrocity crises, to take the necessary action to address them.