Jakob v.H. Holtermann addresses the question whether or not we have reason to believe that the ICC can deter potential perpetrators of international crimes, in particular the crime of aggression taking the Danish and British involvement in the Iraq War as an example, and he believes we have good reason to do so. As a ‘normativist’ he criticises the critics of deterrence, and their, in his view, too demanding burden of proof regarding a deterrent effect: It is not about conclusive evidence, but about levels of probability. And just like in domestic criminal law, we have reason to believe that the threat of international punishment has a deterrent effect. The domestic analogy does not break down, despite the differences between domestic, i.e., ‘ordinary’ and international crimes. In Holtermann’s view these differences should not be exaggerated, and he argues that the main difference lies in the absence on the international level of anything resembling a state’s monopoly of force. In the end, he argues that the ICC is one preventive measure among others, like a slice of Swiss cheese, i.e., with holes, or one component of a ‘broad spectrum’ drug, and that taken together – with other slices of Swiss cheese, or other components of a broad spectrum’ drug – these measures cause a deterrent effect.