Positive Complementarity in Action: International Criminal Justice and the Ongoing Armed Conflict in Ukraine

Abstract Complementarity has been traditionally understood in a twofold manner. On the one hand, the principle of complementarity explicates the jurisdiction of the International Criminal Court. On the other hand, it has been conceptualised as the broader principle that governs the functioning of the international criminal justice system built after the entry into force of the Rome Statute. Understood in this sense, complementarity outlines the interplay between different (domestic and international) accountability actors, including national authorities and civil society. This article explores the ways in which the principle of complementarity has been operationalised in Ukraine since 2014, in an attempt to highlight the challenges faced by domestic and international justice actors in the situation of atrocities being committed in an ongoing armed conflict. It puts forward an argument that ad hoc responses introduced in cooperation and coordination with local and international partners—including the civil society—have been prioritised over permanent legislative solutions. These ad hoc responses have the potential to influence the expansion of the complementarity architecture, shape the coordinated accountability approaches and advance positive complementarity for core international crimes in ongoing armed conflicts.