Many investment arbitration cases involve a challenge to a regulatory measure of a host state on the basis of indirect expropriation. The practice of arbitral tribunals is diverse and unsettled. In recent years States have been trying to clarify the relationship between regulatory freedom (also known as 'police powers') and indirect expropriation by revising provisions on indirect expropriation in their investment treaties. This book provides the first focused analysis of indirect expropriation and regulatory freedom, drawing on a broad range of the jurisprudence of investment tribunals. The nature of regulatory freedom in international law has been explained on the bases of jurisprudence of international courts and tribunals such as the International Court of Justice (ICJ), Permanent Court of International Justice (PCIJ), dispute resolution bodies of the World Trade Organisation (WTO), European Court of Human Rights. While showing how cases involving standoff between regulatory freedom and indirect expropriation can be resolved in practice, the book goes on to present a conceptual framework for interpreting the nuances of this relationship.The book provides a detailed responses to the following complex questions: To what extent do states retain regulatory freedom after entering into investment treaties? What is the scope of regulatory freedom in general public international law? What are the elements of regulatory freedom and standard of review? How to draw a dividing line between regulatory freedom and indirect expropriation? Whether the sole effects doctrine or the police powers is the appropriate method for distinguishing between regulatory freedom and indirect expropriation?While addressing these questions, the author analyses different theoretical approaches that reflect upon the relationship between regulatory freedom and indirect expropriation and how far they assist in understanding these potentially overlapping concepts; their relationship with each other; and the method for distinguishing between them.Given the dense network of around three thousand bilateral investment treaties (BITs) that impose an obligation to protect foreign investments in a State, this book will help practitioners identify, through analysis of cases from diverse fields, how a situation may be categorized either as regulatory freedom or as indirect expropriation. The analysis will also be of value to government officials and lawyers involved in negotiating and re-negotiating investment treaties, and to arbitrators who have to decide these issues. Scholars will welcome the book's keen insight into the contentious relationship between a customary international law norm and a treaty norm.