Many international legal scholars and foreign governments have argued that the recent war in Iraq violated international law. This paper, published as part of an Agora in the American Journal of International Law, criticizes this view on two grounds. It explains that these scholars have failed to properly read existing United Nations Security Council resolutions that authorized the use of force against Iraq. Even putting the United Nations to one side, this paper explains that the use of force could have been justified, at the time of the invasion of Iraq in the spring of 2003, as an exercise of self-defense. It argues that traditional notions of self-defense, which permit the anticipatory use of force before an offensive attack occurs, have changed to take into account the greater magnitude of destruction of weapons of mass destruction and the behavior of rogue states.