This collection explores some of the many ways in which constitutional orders engage with, and are shaped by, their exteriors. Constitutional and legal theory often marginalize 'foreign' elements, such as norms originating in other legal systems, the movement of individuals across borders, or the application of domestic law to foreign affairs. In The Double-Facing Constitution, these instances of boundary crossing lie at the heart of an alternative understanding of constitutions as permeable membranes, through which norms can and sometimes must travel. Constitutional orders are facing both inwards and outwards - and the outside world influences their interiors just as much as their internal orders help shape their surroundings. Different essays discuss the theoretical and historical foundations of this view (grounded in Kelsen, Hobbes, Locke, Rousseau and others), and its contemporary relevance for areas as diverse as migration law, the conflict of laws, and foreign relations law.

Jacco Bomhoff is Associate Professor of Law at the Law Department of the London School of Economics and Political Science. He is the author of Balancing Constitutional Rights: The Origins and Meanings of Postwar Legal Discourse (Cambridge, 2013). David Dyzenhaus is University Professor of Law and Philosophy at the Faculty of Law, University of Toronto, and a Fellow of the Royal Society of Canada. He is the author and editor of several books, including Legality and Legitimacy (1997) and The Constitution of Law (Cambridge, 2006). Thomas Poole is Professor of Law at the Law Department of the London School of Economics and Political Science. He is the author of Reason of State: Law, Prerogative and Empire (Cambridge. 2015), and the editor, with David Dyzenhaus, of books on Hobbes, and on Oakeshott, Hayek and Schmitt.