Book excerpt: Transnational investment involves a variety of actors (States, public and private legal entities, and natural persons) whose relationships are governed by rules and legal instruments belonging to different legal systems. This book provides a systematic study of the sources of rights and obligations in the field of transnational investment, and their coordination and interaction. It focuses primarily on the network of over 3,000 Bilateral Investment Treaties, international investment contracts, customary international law, the main multilateral treaties, national legislation, international case law and general principles of law. The book, firmly based on State practice, arbitral awards and national decisions, is indispensable to fully appraise the nature and content of the claims of private investors as well as to identify the law applicable in investment arbitration.