We have been working together for more than fifteen years. Our engagement with the subject matter of this book began when we were first invited to participate in interdisciplinary seminars bringing together international lawyers and international relations theorists. As lawyers we were in the minority, and were sometimes called upon to explain what practical difference international law made in international society, and often to describe how international legal norms differed from other social norms. International lawyers tend to take for granted the importance of the discipline, but our engagement with related disciplines prompted us to reflect more carefully on what it is that accounts for the effectiveness and distinctiveness of legal norms. Our consequent work has often required that we move outside familiar debates and established conceptual frameworks, and we are grateful for the hard questions that launched our interest in the research agenda that underlies this book.

Our work together would not have been possible without the consistent and generous support of the Social Sciences and Humanities Research Council of Canada. We have benefited from the collegial environments of the Faculties of Law of the University of British Columbia, McGill University and the University of Toronto, as well as sabbatical leaves and further financial support from these institutions. The Connaught Fund of the University of Toronto provided a generous Research Fellowship. We also appreciate the workshop funding provided by the former Canadian Centre for Foreign Policy Development of the Department of Foreign Affairs and International Trade.