This book sheds light on a fascinating process of historic, legal evolution, starting from a situation of doubt as to whether the Community had treaty-making power, and ending with certain treaties being denied to sovereign states and transferred to an international organization. This process is still continuing, and brings in its wake far-reaching results. The author makes distinction between cases where exclusive treaty-making is explicitly specified in the founding treaties, and cases where treaty-making power is implicit, and is derived from the general structure of Community law. Implicit power becomes exclusive only by `occupying the field', which means enactment, and exclusive power negates ab initio the Member States' power, whereas implicit exclusive power merely negates the competence of the Member States to establish rules conflicting with those of the Community. Scholars, practitioners, lawyers, students and everybody who deals with European Union affairs will find this book of great interest.