This book touches upon the main subjects in public international law, with special emphasis on the application of international rules within the national legal orders. The treatment of the matter is based on the practice, particularly on the case law of international and domestic courts. The main characteristic of the book is the very extensive discussion of the role of domestic courts, as well as public officials, in order to achieve the effectiveness of international law. National judges, who are considered the principal addressees of the book, are viewed as a sort of propelling force behind international law to the extent that they use, as far as possible, the means provided by municipal law to ensure compliance with international law.