International crimes, such as crimes against humanity, genocide and war crimes, are committed by individuals. However, individuals rarely commit such crimes for their own profit. Instead, such crimes are often caused by collective entities. Notable examples include the 'dirty war' in Argentina in the 1970s and 1980s, the atrocities committed during the Balkan Wars in the early 1990s and the crimes committed during the ongoing armed conflicts in the Darfur area in Sudan. Referring to Darfur, the Prosecutor of the ICC noted in 2008 that, although he had indicted a few individuals, 'the information gathered points to an ongoing pattern of crimes committed with the mobilisation of the whole state apparatus'. This book reviews the main legal avenues that are available within the international legal order to address the increasingly important problem of system criminality and identifies possible improvements.