Professor Pieter Jan Kuijper has had a mixed career as an academic and a practitioner of International and European Law in the universities of Leiden and Amsterdam and in the European Commission and the WTO Secretariat. His most recent posts in international organizations have been Director of the Legal Affairs Division of the WTO Secretariat and Principal Legal Advisor and Director of the External Relations and Trade Division of the Legal Service of the European Commission. ; Prof. Dr. Jan Wouters is Professor of International Law and International Organizations, Jean Monnet Chair of EU and Global Governance, and Director of the Institute for International Law and the Leuven Centre for Global Governance Studies at the University of Leuven. He is Visiting Professor at the College of Europe (Bruges), at Sciences Po (Paris), at the University of Barcelona, and in the European Master's in Human Rights and Democratisation (EMA, Venice). He is Member of the Royal Flemish Academy of Belgium for Sciences and Arts, has been referendaire at the European Court of Justice and practises law as Of Counsel at Linklaters, Brussels. He is Editor of the International Encyclopedia of Intergovernmental Organizations and Vice-Director of Revue belge de droit international. He has published widely on the EU, international law, and international organizations.; Prof. Dr. Frank Hoffmeister is Deputy Head of Cabinet of the EU Trade Commissioner Karel De Gucht and teaches international economic law at the Free University of Brussels. He has been a long-standing member of the Commission Legal Service, specialised in international and institutional law (2002-2010). He has published widely on European law and international law and was visiting scholar in a number of Universities, including Florence and Oxford. Frank is member of the Editorial Board of the Studies in EU External Relations, edited by Marc Maresceau.; Geert De Baere is Assistant Professor of International Law and EU Law at the Faculty of Law and Senior Member of the Leuven Centre for Global Governance Studies, University of Leuven. He studied law at the University of Antwerp and at King's College, Cambridge. His research interests include the legal organization of EU external relations, the relationship between EU law and international law, comparative constitutional law, including comparative federalism, and the philosophy of EU law and international law. His publications include Constitutional Principles of EU External Relations (2008) and (with Cloots, E, and Sottiaux, S, eds), Federalism in the EU (2012). ; Thomas Ramopoulos is an EU lawyer. He studied law (Hons) at Aristotle University of Thessaloniki and further completed a Master of Philosophy in International Relations at the University of Cambridge. He has been a junior researcher at the Leuven Centre for Global Governance Studies since 2011 and he is pursuing a PhD on The Internationalisation of EU Law at the University of Leuven.