This book expands upon research into the protection of foreign investments, which is currently an intensively studied area of international law. At the same time, it also examines environmental protection, as well as general areas of debate in international law, including fragmentation, self-contained regimes, the role of interpretation and of principles, and theories of indeterminacy. In this detailed and concise monograph, the author examines the problematic impact of environmental issues on international investment law from the perspective of arbitral dispute settlement and treaty-making. Current debates concerning 'self-contained' regimes and international law form the background to this investigation. By extrapolating insights from the vast and heterogeneous amount of available practice, the book provides an order to the two spheres of values, from internal and fragmentary approaches to systemic forms of integration. Finally, it outlines a possible method for reconciling investor rights and environmental concerns, which is centred around the model of exceptions and highlights the role of legal principles. This book is essential reading for academics of international investment law and related matters, with useful research material for both practitioners and policy-makers. Moreover, the innovative approach of this book makes it appropriate for adoption in specialised undergraduate and postgraduate courses in international economic law.