This book addresses the topical question how national and international environmental concerns could be adequately integrated into international investment law. It covers the question whether international investment law restricts state sovereignty in an unacceptable way, in particular the freedom of host states to develop national policies and regulation for the improvement of the environment. This book first analyzes the interaction between international investment law and the protection of the environment on the basis of concepts such as sustainable development, fair and equitable treatment, and international responsibility. Secondly, several chapters discuss challenges which are encountered in attempts to integrate environmental concerns in investment policies in specific sectors and regions (e.g. climate change, water pollution, renewable and nuclear energy, and the European Union region). And, thirdly, specific case studies illustrate the legal and policy tensions between investment law and environmental protection, namely Vattenfall's disputes with Germany, legal clashes between Chevron and Ecuador, and multinational mining companies' conflicts in Indonesia.The contributions are written by international experts in this field and are of interest to valuable for policy makers and practitioners, who can use the insights provided as a guide in their work.