Despite a recent explosion of interest in the ethics of armed conflict, the traditional just war criterion that war be waged by a legitimate authority has received relatively little attention. Moreover, of those theorists who have addressed the criterion, many are deeply skeptical about its moral significance. This article aims to add some clarity and precision to the authority criterion and the debates surrounding it, and to suggest that this skepticism may be too quick. The first section analyzes the authority criterion and reveals that there are at least two distinct moral claims associated with it, each requiring separate evaluation. The second section outlines an increasingly influential reductivist approach to just war theory, explain...