Chapter 3 explores the structure of the international criminal justice field. Specifically, the chapter argues that the community of international criminal law practice, which includes judges, lawyers, academics, non-governmental organizations, and state diplomats, is bound by two core norms, or shared understandings: firstly, that the perpetrators of mass atrocities deserve to be punished (the ‘anti-impunity’ norm), and secondly, that punishment should follow a fair criminal process (the ‘legalism’ norm). Next, Chapter 3 turns to the debates taking place inside the international criminal justice field in relation to questions of individual criminal responsibility. The analysis reveals a variety of competing views on the meaning of criminal responsibility rules, on the requirements of a ‘fair process’, and on the mechanisms for ending impunity for mass atrocities. These clashes of ideas result not only from differences in the professional backgrounds of the persons engaging in international criminal law practice, but also from the lack of agreement on the nature of personal culpability for atrocity crimes and on the function of criminal law in the international society.