In this well-researched and detailed book, the authors provide an extensive and critical analysis of post-Soviet regional integration. After almost two decades of unfulfilled integration promises, a new - improved and functioning - regime emerged in the post-Soviet space: the Eurasian Customs Union between Russia, Belarus and Kazakhstan (ECU). The contributors seek to explain this puzzling and politically significant development by examining the ECU's origins, institutional architecture, key driving forces and emerging implications. Their investigation reveals that the ECU is an ambitious and fast moving project in deep economic integration, yet its legal design is complex and member states are driven by a precarious balance of diverse motives. Nevertheless, as the contributions to the volume indicate, the emergence of the ECU already carries important external implications, especially for EU's strategy in the post-Soviet space. Being the first comprehensive and systematic study of the new Eurasian economic integration regime, this book will appeal to academics and students of regional integration, international relations and international law, Russian studies, Post-Soviet politics, as well as Central Asian studies.