The Fragmentation of International Law and Its Implications for Nigeria’s Engagement with Multiple International Legal Regimes

This dissertation theoretically and empirically examines the fragmentation of international law and its consequences for Nigeria's engagement with overlapping and potentially conflicting international legal regimes spanning trade, investment, human rights, environmental, and security law. The fragmentation thesis, analysed by the International Law Commission's Study Group in 2006, identifies the proliferation of specialised international legal regimes as a source of normative inconsistency, jurisdictional conflicts, and differential obligations that creates particular challenges for developing states with limited legal capacity. Using an original analytical framework developed from Koskenniemi's constitutionalist critique, the ILC fragmentation report, and systems theory, this research develops a fragmentation impact assessment tool applicable to Nigeria's treaty commitments and applies it across a dataset of over 200 international agreements to which Nigeria is party. It fills a critical gap in the literature by shifting fragmentation analysis from its traditional European focus to an African developing state context, generating original empirical findings on fragmentation costs for Nigeria. The dissertation identifies specific legal conflicts between Nigeria's investment treaty obligations, environmental treaty commitments, and human rights obligations, and proposes priority resolution rules. Findings demonstrate that Nigeria bears disproportionate fragmentation costs due to limited domestic legal capacity to manage competing international obligations and recommends institutional reform measures. An original fragmentation management model for developing states is proposed as the dissertation's primary theoretical contribution. Keywords: fragmentation, international law, Nigeria, treaty obligations, legal pluralism.