Patrick Dumberry is an Associate Professor at the Faculty of Law (Civil Law Section), University of Ottawa. From 1998 to 2009, he practiced international law and investor-State arbitration at law firms in Geneva (Lenz and Staehelin, and Lalive) and Montreal (Norton Rose Fulbright) as well as at Canada's Ministry of Foreign Affairs and International Trade (Trade Law Bureau). He completed his PhD in international law at the Graduate Institute of International Studies in Geneva, Switzerland, in 2006. He is the author of more than fifty publications in the fields of international investment law and international law, including State Succession to International Responsibility (2007) and The Fair and Equitable Treatment Standard: A Guide to NAFTA Case Law on Article 1105 (2013).

'The book is a useful guide to a persistently difficult area of law and will be useful for practitioners, academics, and others interested both in the interaction between BITs and customary international law and the role of customary international law in international investment law.' Fabien Gelinas and Lucas Clover Alcolea, Transnational Dispute Management

• Introduction; 1. The concept of customary international law; 2. Dancing with the sources: the fascinating story of the relative importance of custom and treaties at different times in the evolution of international investment law; 3. State practice; 4. Opinio juris; 5. The fundamental importance of customary rules in international investment law; General conclusion.

Patrick Dumberry is an Associate Professor at the Faculty of Law (Civil Law Section), University of Ottawa. From 1998 to 2009, he practiced international law and investor-State arbitration at law firms in Geneva (Lenz and Staehelin, and Lalive) and Montreal (Norton Rose Fulbright) as well as at Canada's Ministry of Foreign Affairs and International Trade (Trade Law Bureau). He completed his PhD in international law at the Graduate Institute of International Studies in Geneva, Switzerland, in 2006. He is the author of more than fifty publications in the fields of international investment law and international law, including State Succession to International Responsibility (2007) and The Fair and Equitable Treatment Standard: A Guide to NAFTA Case Law on Article 1105 (2013).

'The book is a useful guide to a persistently difficult area of law and will be useful for practitioners, academics, and others interested both in the interaction between BITs and customary international law and the role of customary international law in international investment law.' Fabien Gelinas and Lucas Clover Alcolea, Transnational Dispute Management

• Introduction; 1. The concept of customary international law; 2. Dancing with the sources: the fascinating story of the relative importance of custom and treaties at different times in the evolution of international investment law; 3. State practice; 4. Opinio juris; 5. The fundamental importance of customary rules in international investment law; General conclusion.

Patrick Dumberry is an Associate Professor at the Faculty of Law (Civil Law Section), University of Ottawa. From 1998 to 2009, he practiced international law and investor-State arbitration at law firms in Geneva (Lenz and Staehelin, and Lalive) and Montreal (Norton Rose Fulbright) as well as at Canada's Ministry of Foreign Affairs and International Trade (Trade Law Bureau). He completed his PhD in international law at the Graduate Institute of International Studies in Geneva, Switzerland, in 2006. He is the author of more than fifty publications in the fields of international investment law and international law, including State Succession to International Responsibility (2007) and The Fair and Equitable Treatment Standard: A Guide to NAFTA Case Law on Article 1105 (2013).

'The book is a useful guide to a persistently difficult area of law and will be useful for practitioners, academics, and others interested both in the interaction between BITs and customary international law and the role of customary international law in international investment law.' Fabien Gelinas and Lucas Clover Alcolea, Transnational Dispute Management

• Introduction; 1. The concept of customary international law; 2. Dancing with the sources: the fascinating story of the relative importance of custom and treaties at different times in the evolution of international investment law; 3. State practice; 4. Opinio juris; 5. The fundamental importance of customary rules in international investment law; General conclusion.