In original essays written by both senior scholars as well as rising younger scholars in the field of international ethics, this volume addresses the ethics of war in an era when non-state actors are playing an increasingly prominent role in armed conflict. Central to this concern is the issue of whether, or under what conditions, non-state actors can be said to have the "authority" to participate in war. The contributors therefore explore and analyze the problems with, and possibilities for, incorporating non-state actors into the traditionally state-centric moral vocabulary about war - namely, the just war tradition.