Vademecum of International law, as the label of this textbook indicates, is a brief handbook of public international law. The objective of this textbook is to provide its readers with a coherent introduction into the study of public international law. This textbook therefore explains the main concepts and institutions of public international law. In doing so, where appropriate, the text takes into consideration historic origins and development of the respektive institutions of public international law, as well as the historic development of public international law as a whole. This textbook also deliberately includes extensive quotations of both primary texts (such as court decisions or texts of international treaties) as well as thoughts of influential writers in the respective fields of public international law. The resort to extensive quotations should provide the reader with first hand resources without the (always subjective) deformation of the respektive source via paraphrasing. This textbook is not intended to serve as an all-encompassing textbook or encyclopedia. After all, for that it would be too short in the first place. The objective here is to provide the reader with a basic introduction into the key areas of public international law, foundations upon which one can built further study. The reason is that this book is primarily intended as a main textbook for a one semester course called Introduction to Public International Law taught at the University of West Bohemia in Pilsen and frequented primarily by Erasmus exchange students for whom English is in most cases a foreign language. In doing so, this textbook leaves out certain areas of public international law that ought to be read elsewhere, inter alia: material maritime law, international criminal law, space law, aviation law, international environmental law, and human rights law. Other areas are discussed in volume and depth appropriate to a one semester course in a qualifying law degree program.