Revisiting The Principle of Complementarity: A Critical Analysis of Tanzania’s Engagement with International Criminal Justice Mechanisms

The evolution of international criminal justice has significantly reshaped the global approach to accountability for serious international crimes. Central to this framework is the principle of complementarity, which governs the relationship between national jurisdictions and international mechanisms, particularly the International Criminal Court (ICC). This principle establishes that states retain primary responsibility for prosecuting international crimes, while the ICC acts as a court of last resort where domestic systems are unwilling or unable to act. This article critically examines the application of the principle of complementarity in the context of Tanzania. It argues that despite the normative acceptance of complementarity within international criminal law, Tanzania’s legal and institutional framework remains insufficient to effectively operationalise this principle. The study adopts a doctrinal and analytical methodology, drawing on international legal instruments, domestic legislation, and relevant scholarly literature. The findings reveal significant gaps in Tanzania’s domestic legal framework, including the absence of comprehensive legislation incorporating international crimes, limited institutional capacity, and challenges related to political will and resource constraints. These shortcomings undermine the effective implementation of complementarity and risk perpetuating impunity. By situating Tanzania within the broader African experience, the article contributes to ongoing scholarly debates on the implementation gap between international criminal justice norms and domestic legal systems in developing states. It further enriches international criminal law scholarship by demonstrating how structural and institutional limitations shape the practical effectiveness of complementarity in emerging legal systems. The article concludes by emphasising the need for targeted legal and institutional reforms to strengthen Tanzania’s engagement with international criminal justice mechanisms and to ensure meaningful accountability for serious crimes under international law.