Over the last decade, theorists have persistently criticised the assumption that the International Criminal Court (ICC) can produce a noteworthy deterrent effect. Consequently, consensus has emerged that we should probably look for different ways to justify the ICC or else abandon the prestigious project entirely. In this paper, I argue that these claims are ill founded and rest primarily on misunderstandings as to the idea of deterrence through punishment. They tend to overstate both the epistemic certainty as to and the size of the deterrent effect necessary in order to thus justify punishment. I argue that we should in general expect reasonably humane punitive institutions to lead to better consequences than if we abolish punishment entirely, and I show that, contrary to widespread assumption among critics of the ICC, we should not expect the conditions characteristically surrounding mass atrocity to undermine this presumption. Properly understood, the ICC equals adding another “slice of cheese” to our comprehensive crime preventive system modelled along the lines of James Reason’s Swiss cheese model of accident causation and risk management. Undoubtedly, some future perpetrators will elope through the holes in this layer too, but others will be deterred.