This article applies the traditional just war criteria of just cause, necessity, and proportionality to the use of force by police officers. After describing the origins and structure of the just war perspective, it details how those core criteria can be used to construct a normative account of police force, which, in turn, can be used to diagnose a variety of misconceptions that have helped shape, and continue to shape public discourse about police violence in the United States. On the account presented here, the use of force by police officers is justified if and only if the level of force used is necessary to secure compliance with a legal command (or in defense of self or others), and will not result in more harm than good all things considered. What becomes apparent is that many common beliefs and attitudes about police force are mistaken—e.g., that a suspect’s criminality, disrespectful behavior, or even use of lethal force automatically renders him liable to police force, or that police force is proportionate so long the amount of force used does not grossly exceed that used by the suspect. It concludes that, relative to the appropriate ethical standards, much if not most police force used at present is unjustified.