International criminal law (ICL) is dedicated to the battle against impunity. However, the concept of impunity lacks clarity. Providing that clarity also reveals challenges for the current state and future prospects of the project of ICL, which this article frames in cosmopolitan terms. The ‘impunity norm’ of ICL is generally presented in a deontic form. It holds that impunity for perpetrators of international crimes is a wrong so profound that states and international bodies have a pro tanto duty to prosecute and punish perpetrators, a duty that cannot be overridden by considerations of cost, including the costs of infringing on the traditionally understood legal sovereignty of states. This deontic reading of the impunity norm is difficult to justify, a fact linked to the waning fortunes of ICL over the past several years. If ICL is to reverse this trend, the impunity norm’s strongly deontic reading should be replaced by a version derived from deliberative principles.
