About the Author: Manuel Kellerbauer, Member of the Legal Service, European Commission, Marcus Klamert, Senior Lecturer, Vienna University of Economics and Business, Jonathan Tomkin, Member of the Legal Service, European Commission Manuel Kellerbauer is a Member of the Legal Service of the European Commission, and lectures on competition law at the Europa Institute of Saarland University. Marcus Klamert is a Member of the Legal Service at the Federal Chancellery of Austria and a senior lecturer at the Vienna University of Economics and Business. He is the author of The Principle of Loyalty in EU Law (OUP, 2014). Jonathan Tomkin is a Member of the Legal Service of the European Commission, and co-authored The EU Citizenship Directive (with E Guild and S Peers, OUP, 2014).