This chapter presents an account of how international law functions in relation to international relations. First, it surveys the sources and philosophical underpinnings of international law. Second, it outlines the scope of subjects addressed by international law. Third, it considers some of the ways international law impacts on Australia. Finally, it addresses the question of whether international law really matters in international relations.
International law began as a system of law governing relations among states. It has evolved in conjunction with the evolution of the international states-system so as to encompass the activities of intergovernmental organisations, multinational corporations, not-for-profit non-governmental organisations and individuals. It is essential for students of world politics to learn about the functioning of the international legal system because international law is integral to world politics. The breadth of the subject matter encompassed by international law and the increasing complexity of the international legal system mean, however, that even international lawyers often specialise in only a few aspects of international law and whole books are devoted to single topics in international law. This chapter does not attempt to cover all the content of international law but to introduce the reader to how the system of international law functions and to offer guidance as to where to find information on particular subject areas of international law when the need arises.