This chapter outlines the policies and practice of the Office of the Prosecutor on complementarity. It argues that complementarity has two dimensions: an admissibility dimension and a second, related dimension, ‘positive complementarity’. Due to its mandate, the ICC will deal only with a few cases over the years. But the impact of its cases and rulings (the ‘shadow of the law’) extends to a multiplicity of entities, including States Parties and non-states parties. The purpose, efforts and the impact of the Court are thus indicative of progress towards establishing a global criminal justice system.

The Rome Statute as the foundation of a global criminal justice system

The goal of the Rome Statute is to end impunity for the most serious crimes of concern to the international community as a whole and to contribute to their prevention. To achieve its goal of holding accountable the perpetrators of such crimes, the Statute created an interdependent, mutually reinforcing system of justice with a permanent International Criminal Court (ICC) complementary to national criminal jurisdictions. The Statute, in its Preamble, recalls ‘the duty of every State to exercise its criminal jurisdiction over those responsible for international crimes’, thereby giving states the primary responsibility for preventing and punishing atrocities. Proceedings before the ICC, as court of last resort, should remain an exception to the norm.