This book provides a brief overview of the historical roots of the International Criminal Court and explains the unique character and purpose of the principle of complementarity within the Rome Statute and its other constituent instruments. The author also examines article 17, the core provision in relation to complementarity, and describes its application in different phases of the proceedings before the ICC. This study tries to highlight the problematic issue of amnesties, which is not covered by the respective legal instruments, and questions the political and judicial implications of complementarity. This book is intended as a practical handbook rather than a theoretical inquiry.