Belgian national, trained as a lawyer and has a specialist degree in international and European law from the Catholic University of Leuven. He was rapporteur for the studies conducted by the Florence based European University Institute on the reorganisation of the Treaties and the treaty amendment procedures and on the staff of Belgium’s Permanent Representation to the European Union during the Intergovernmental Conference that led to the Treaty of Amsterdam. From 2002 to 2004 he was a member of the European Commission Group of Policy Advisers assigned to the Convention Secretariat. He is currently visiting Professor at the University of Paris I Panthéon-Sorbonne. He is the author of several academic publications on constitutional developments in the European Union, addressing in particular the allocation of competences within the Union, subsidiarity, differentiated integration (reinforced cooperations) and institutional reforms.