Sovereignty is a foundational idea upon which regional organisation of nations is built, yet its demise has often been predicted. Regionalism, which commits states to common frameworks such as rules and norms, tests sovereignty as states relinquish some sovereign power to achieve other goals such as security, growth, or liberalisation. This book examines the practice of normative contestation over sovereignty in two regional organisations of Africa and Asia – the AU and ASEAN. A structured comparison of three case studies from each organisation determines whether a norm challenging sovereignty was accepted, rejected, or qualified. Ng has carried out interviews about, and detailed analysis of, these six cases that occurred at formative moments of norm-setting and that each had very different outcomes. This study contributes to the understanding of norms contestation in the field of international relations and offers new insights on how the AU and ASEAN are constituted.