The past decade has seen a veritable explosion of investment treaty and other arbitration claims brought against sovereigns. Many of those cases have been filed before the International Centre for Settlement of Investment Claims (ICSID), which has its own self-contained rules for enforcement. Given this significant increase in sovereign cases and the issues attendant to sovereign immunity, this treatise is timely in addressing the various issues that arise in enforcing arbitral awards against sovereigns. One of the first questions posed to their counsel by clients considering the initiation of an arbitration proceeding against a sovereign state is whether and how the resulting award can be enforced. The origin of the client’s question is usually based in some knowledge that a state possesses sovereign immunity, along with an uncertain concern about the exceptions to such immunity and the difficulties of enforcement against a sovereign’s assets. This uncertainty is understandable, especially in light of the sometimes confusing and even contradictory court decisions in certain jurisdictions. It is these inquiries in their broadest application that form the subject of this treatise. With contributions by eminent and experienced practitioners of the multiple issues that have arisen in various jurisdictions and the key cases that have created the law of enforcement of obligations against sovereigns, this book will provide access to valuable information, add to the transparency of this subject and further spur the consistent development of this area of law. This book is divided into three parts. The first part is general in nature and includes chapters encompassing the subjects of sovereign immunity in general (including both immunity from jurisdiction and immunity from enforcement), treaty obligations to honor awards, diplomatic protection by a claimant’s government to obtain payment of awards, and conciliation and settlement. The second part of the book deals with the means of enforcing awards. Part three of this treatise addresses the enforcement issues that arise in specific jurisdictions in which enforcement against sovereign assets is often sought - in particular, the United States, the United Kingdom, Switzerland, France, The Netherlands, and South America.