This book explores the normative foundations of ASEAN and the EU. It revives the history of the two organizations in an in-depth narrative of the protracted arguments surrounding their establishment, legal integration and enlargement. While political actors used norms to legitimize their ideas for institutional change, the complex and dynamic nature of these norms also provided the breeding ground for contestation and, sometimes, institutional sclerosis and failure. Recasting these processes in an innovative English School framework, the volume makes a crucial contribution to the literature of Comparative Regionalism that goes beyond Eurocentric perspectives.