Christian Calliess is Professor for Public and European Law at Freie Universität Berlin, Germany. From 2015 until 2018 he was on leave in order to work as Legal Adviser to the European Political Strategy Center (EPSC), the In-House-Think-Tank of the President of the European Commission, and Head of the Institutional Team. Before 2015 he advised the German Parliament (Bundestag), also representing it before the German Constitutional Court and the Court of the EU, among others in the ESM- and OMT-Case. He co-edits a Commentary on European Law and has regularly published on matters of European, constitutional and environmental law. Gerhard van der Schyff is an Associate Professor in the Department of Public Law and Governance at Tilburg Law School in the Netherlands. His research interests cover European and comparative constitutional law and fundamental rights. Gerhard's research has been referred to in various (minority) opinions, including by the European Court of Human Rights and the Supreme Court of Appeal of South Africa. In 2015, he held a Humboldt Fellowship for Experienced Researchers at the Chair of Professor Christian Calliess at the Freie Universität Berlin.