The ECOWAS and AU peace and security legal frameworks have attracted little study amongst international law scholars despite its far-reaching normative innovations and implications for Africa, the UN Charter-based law of humanitarian intervention and international law in general. With the exception of a couple of writers, the few studies that exist have dismissed such provisions as article 4(h) of the AU Constitutive Act and article 10 and 25 of the ECOWAS Mechanism for Conflict Prevention, Management, Resolution Peacekeeping and Security Protocol (MCPMRPS) as illegal treaties because of their incompatibility with articles 2(4), 24(1), 53(1) and 103 of the Charter. None of these studies examined the theoretical basis of these treaties and at a time the world is in search of a legal framework for the operationalisation of the Responsibility to Protect (R2P), it has become imperative to undertake an interrogation of the theoretical underpinnings of these treaties. My study tested the legal validity of the AU–ECOWAS intervention instruments using two theoretical frameworks: transformations of world constitutive process of authoritative decision and the illegal international legal reform theories. It also examined the validity of the treaties under conventional and customary international law. The book advanced three main arguments: