Jaap W. de Zwaan is Professor of the Law of the European Union at the Law School of Erasmus University Rotterdam and Vice-President of the Executive Board and Member of the Governing Board of the T.M.C. Asser Institute. Jan H. Jans teaches EU law at the University of Amsterdam and the University of Groningen. Frans A. Nelissen is General Director of the T.M.C. Asser Institute and Professor of International Environmental Law, University of Groningen. Steven Blockmans is researcher on the law of the European Union, T.M.C. Asser Institute, The Hague.