This strongly interdisciplinary book provides a first tentative evaluation of the role that geopolitics plays in shaping the genesis and functioning of the law of EU Common Foreign and Security Policy (CFSP). It introduces the reader to the geopolitical context of the EU and of its main neighbours, as well as to the legal architecture of CFSP. The book then presents selected cases of the Union’s action (or inaction) in CFSP since 2009. These show the key argument of the book: the law of CFSP is not entirely fit for purposes as it does not reflect the geopolitical reality of the continent. The book reflects on such geopolitical reality as it results, in particular, from the 2004 EU enlargement, and comments upon three key issues of the CFSP legal framework: issues of coherence, accountability, and effectiveness. With its fusion of law and geopolitics, the book will be invaluable for students of EU foreign policy and EU external relations law.