This book explores the theoretical origins, historical foundation, political meaning, and legal development of western constitutionalism, as well as the structure and transformation of constitutional law in the Western World. Introducing the historical background of western constitutional traditions, it links this rich, conceptual framework with the legal arrangements of states’ constitutions and the current trends of the internationalization of constitutional law. Serving as a comprehensive introduction to constitutional studies, this book provides detailed information on the design of legal systems, while addressing the main critical, theoretical issues raised by constitutionalism in western democracies and in the global landscape. This new, third edition covers a broader scope, reflecting recent political and legal transformations, and is enriched in terms of didactic instruments for university students.