He served as the Legal Counsel of the European Council and the Council of the EU and Director General of the Council’s Legal Service from 1988 to 2010. He is an Honorary French Conseiller d’Etat, a former diplomat at the UN and the former Director of Legal Affairs of the OECD. He was the Legal Adviser to the successive intergovernmental Conferences which negotiated and adopted the treaties of Maastricht, Amsterdam and Nice, the Constitutional Treaty and, finally, the Lisbon Treaty.