One might expect the opening chapter of this Cambridge Companion to International Criminal Law to suggest that human rights came first and slowly developed a criminal law arm in order to prosecute the worst offenders. Indeed, a well-established account presents the process as passing from a preliminary enunciation of values stage through to declarations, prescription, enforcement, and finally criminalisation. But the relationship between human rights and international criminal law is more complicated and, today, produces not only tension but also confrontation. This chapter will highlight tension over harmony, and suggest that the articulation of the relationship between these two branches of law remains very much ‘work in progress’. Although many scholars and activists are involved in both branches, at certain points the dynamics diverge and the thirst for the prosecution of international crimes may not always take fully on board the human rights implications of such processes.

International criminal law can be seen as covering both crimes under treaties, which usually take effect through national legal orders, as well as what are increasingly called ‘atrocity crimes’ or ‘core crimes’, which may exist independently of national law and can be prosecuted in international courts. Such atrocity crimes can of course also be prosecuted at the national level, where the national courts enjoy such jurisdiction.

International criminal law, in the form of treaty crimes, has been traced back to classical times and to a treaty between the Kings of Cyprus, Alexandria, Egypt, Cyrene, and Syria aimed at preventing the harbouring of pirates. The modern idea of international criminal law owes more, however, to the International Military Tribunals, established in Nuremberg and Tokyo after the Second World War. These courts, set up by the victorious Allies, focused on atrocity crimes (war crimes, crimes against humanity and genocide) as well as crimes against peace (aggression).

Strictly speaking, the Nuremberg International Military Tribunal had concluded its work before the drafting of the 1948 Universal Declaration of Human Rights had been completed. So it might seem that international criminal law came before international human rights law. But such a conclusion would ignore the key point that multiple commitments to fight for human rights were made by the Allies and popular movements throughout the Second World War.