International law is now of potential concern to all lawyers. Even subjects which seem purely of national or domestic concern can be affected by public international law, such as where new law is derived from treaties or where issues have international aspects. Students and lawyers therefore need to study international law as much for its practical effects and consequences within national legal systems as for its more widely-known role in relations between states and its geo-political significance. This book concentrates on the concepts and core areas of public international law, as well as the skills which students and lawyers need to acquire in order to study and work with international law, whether generally or in specialist areas.