This book outlines the principles behind the international law of foreign investment. The main focus is on the law governed by bilateral and multilateral investment treaties. It traces the purpose, context, and evolution of the clauses and provisions characteristic of contemporary investment treaties, and analyses the case law, interpreting the issues raised by standard clauses. Particular consideration is given to broad treaty-rules whose understanding in practice has mainly been shaped by their interpretation and application by international tribunals. In addition, the book introduces the dispute settlement mechanisms for enforcing investment law, outlining the operation of Investor-State arbitration. Combining a systematic analytical study of the texts and principles underlying investment law with a jurisprudential analysis of the case law arising in international tribunals, this book offers an ideal introduction to the principles of international investment law and arbitration, for students, scholars, and practitioners alike.