The complementarity of the International Criminal Court (ICC) is one of the fundamental principles of the Rome Statute for the International Criminal Court. The principle of complementarity is the parameter which defines the relationship between States and the ICC. It provides that cases are admissible before the ICC if a State remains wholly inactive or is 'unwilling' or 'unable' to investigate and prosecute genuine cases of genocide, crimes against humanity and war crimes. The Amsterdam Center for International Law and the Department of Legal Philosophy at the Law Faculty of the Free University of Amsterdam held an international expert roundtable on the 'Complementarity Principle of the Rome Statute of the International Criminal Court' on 25 and 26 June 2004. This book contains contributions on complementarity, which were presented and discussed during that meeting. They analyse the principle from theoretical, practical and conceptual perspectives.