This is a book about international criminal law. More specifically, this book is an investigation of the regime of international criminal law enforcement that has been created since the late 1980s. This is a regime which involves both national and international forums for the prosecution of international crimes. This study is essentially in two parts: part I (chapters 1–3) explains the development of the regime, and some of the problems it has encountered. Having established the existence of the regime, part II (chapters 4–6) will evaluate the regime from the point of view of its legitimacy and compliance with the rule of law, with respect both to who is prosecuted and the approaches taken to the applicable substantive law.

There are a number of different understandings of the content of ‘international criminal law’. There is no single right answer as to what is included in ‘international criminal law’: the phrase may mean different things to different people. Writers such as M. Cherif Bassiouni take an ‘omnibus’ approach to the subject, including any crime which fulfils one of ten criteria, encompassing having a treaty which includes a duty or right to extradite. This is a very broad approach. The approach taken in this book is narrower than Bassiouni's. International criminal law is taken to be that body of international law that imposes criminal responsibility directly upon the individual, without the necessary interposition of national legal systems.