This book provides a critical analysis of the definitions of war crimes and crimes against humanity as construed in the Rome Statute of the International Criminal Court. Each crime is discussed from its origins in treaty or customary international law, through developments as a result of the jurisprudence of modern ad hoc or internationalised tribunals, to modifications introduced by the Rome Statute and the Elements of Crimes. The influence of human rights law upon the definition of crimes is discussed, as is the possible impact of State reservations to the underlying treaties which form the basis for the conduct covered by the offences in the Rome Statute. Examples are also given from recent conflicts to aid a ‘real life’ discussion of the type of conduct over which the International Criminal Court may take jurisdiction. This will be relevant to postgraduates, academics and professionals with an interest in the International Criminal Court and the normative basis for the crimes over which the Court may take jurisdiction.