Can there be a crime of internal aggression?

Aggression is usually conceived as a phenomenon of inter-state relations. However, this view seems lacking in an era in which most-and certainly the deadliest- wars are conflicts within States. Yet, much in line with the general view in international law that there is no internal jus ad bellum, there is no international norm that criminalizes, in a straightforward manner, the wrongful resort to armed force within States. Crucially, if the normative core of the crime of aggression is to address the unjust killings that it entails-including killings that might be lawful under jus in bello-then the absence of an internal equivalent of aggression reflects an inconsistency. This chapter, therefore, offers a preliminary discussion of a crime of internal aggression. Building on a previouswork, it argues that international human rights law can serve as an internal equivalent of jus ad bellum. It then discusseswhether existing international criminal law captures wrongful killings that do not violate international humanitarian law, when these occur in internal conflicts. Arguing that the answer is negative, this chapter imagines a crime of internal aggression, applicable both to the leaders of States and of armed opposition groups.