The Complementarity Principle and the Politics of International Criminal Justice: A Case Study of the ICC’s Nigeria Examination

This study examines the operation of the complementarity principle under the Rome Statute through an in-depth case study of the ICC's preliminary examination into the situation in Nigeria, which was maintained for over a decade before being elevated to a full investigation. The complementarity principle, which holds that the ICC may only exercise jurisdiction where national courts are unwilling or unable genuinely to investigate and prosecute Rome Statute crimes, is the fulcrum of the ICC's relationship with state parties and a key test of the international criminal justice system. Using analytical legal methodology combined with process tracing, the research examines the ICC Office of the Prosecutor's reports on Nigeria between 2010 and 2023, the domestic prosecutions that Nigeria advanced as evidence of complementarity compliance, and the normative standards the OTP applies in assessing genuine proceedings. The paper interrogates the political dimensions of the complementarity assessment, examining how diplomatic considerations and Nigeria's status as an influential African state affected the pace of the examination. It fills a research gap by systematically testing the consistency of the OTP's Nigeria assessment against the complementarity standards applied in Uganda, DRC, and Kenya. Findings indicate that the Nigeria examination reveals systemic tensions in complementarity doctrine between legal objectivity and geopolitical pragmatism, contributing to normative uncertainty. The study makes an original contribution to complementarity scholarship by developing a structured analytical checklist for OTP preliminary examination assessments. Keywords: complementarity, ICC, Rome Statute, Nigeria, preliminary examination.