Our collaboration on this book began as a conversation about the European Court of Justice (ECJ) and its role in the process of European integration. Over the last fifteen years, that conversation prompted us to engage broader theoretical questions about the impact and limits of international courts. It also incited our effort to collect and examine evidence that would allow us to distinguish how and under what conditions international courts (and the ECJ in particular) shape the behavior of their member states. This book represents the current state of that (now very long) conversation. In executing this project, we have been very fortunate to receive the generous financial support of several organizations. The National Science Foundation (SES-079084) provided funding for the collection of data regarding rulings by the ECJ and the development of our theoretical account. The University of Kentucky and the Halle Institute at Emory University also contributed financially to the data collection. The John Simon Guggenheim Foundation provided Dr. Gabel with a fellowship to write a large portion of this manuscript. Caitlin Ainsley, Don Beaudette, Bethany Blacktsone, Marc Hutchison, Michael Malecki, Toby Rider, and Joe Sonka provided valuable research assistance. Wehave had the opportunity to present various parts of the book at a number of conferences and seminars. We are particularly grateful for the hospitality and comments from the seminar participants at the European Union Centers at the University of Colorado and Syracuse University; the schools of law at the University of California–Berkeley, Georgetown University, University of Texas, Hebrew University of Jerusalem, and Tel Aviv University; the Europe Center at Stanford University and Duke University; the departments of political science at the University of Colorado, Duke University, the University of Georgia, the University of South Carolina, the University of Wisconsin, the University of Rochester, and SUNY-Buffalo. vii