This book offers an authentic and original perspective on the principles of solidarity and rule of law that are variously interconnected and increasingly invoked in international relations and affairs, especially in the context of the European Union, where they are among the founding values common to all Member States. The innovative approach the authors adopt consists in the joint reading of these two principles within the broader framework of EU security, thus offering a new interpretation and fertile ground for further research. Divided into four parts, the authors consider EU security to be linked to the implementation of both these principles, particularly with regard to EU stabilization and enlargement to the Western Balkans, cross-border security, migration and asylum management, criminal justice and human rights, and police and judicial cooperation The contributions of eminent scholars, international experts, and practitioners are the book’s greatest strength. In addition, it offers a valuable new perspective on the study of contemporary issues affecting the Western Balkans, but also all Member States and the Union itself. Therefore, the book is an essential resource for students and scholars of EU law, but also for lawyers and professionals involved in criminal proceedings or working in the field of human rights.