In this volume, the third in his trilogy on the philosophical and legal aspects of war and conflict, Larry May locates a normative grounding for the crime of aggression—the only one of the three crimes charged at Nuremberg that is not currently being prosecuted—that is similar to that for crimes against humanity and war crimes. He considers cases from the Nuremberg trials, philosophical debates in the Just War tradition, and more recent debates about the International Criminal Court, as well as the hard cases of humanitarian intervention and terrorist aggression. May argues that crimes of aggression, sometimes called crimes against peace, deserve international prosecution when one State undermines the ability of another State to protect human rights. His thesis refutes the traditional understanding of aggression, which often has been interpreted as a crossing of borders by one sovereign state into another sovereign state. At Nuremberg, crimes against humanity charges were only pursued if the defendant also engaged in the crime of aggression. May argues for a reversal of this position, contending that aggression charges should be pursued only if the defendant’s acts involve serious human rights violations.