[3] He argued sanctions cases before the European Courts including the Dinamo Minsk litigation concerning EU sanctions against Belarus,[4] and the cases OAO Minskii Avtomobilnyi Zavod [5] and Belaz-upravljajusaja kompanija holdinga Belaz Holding v Council.
He was a lecturer in EU and public international law at Leiden University under Professor Henry G. Schermers 1980–1984.
[13] Amongst the works with which he is most associated are “Mixed Agreements” (with Professor Henry G. Schermers), Kluwer, Legal Issues of the Maastricht Treaty (Chancery Law Publishing, 1994) and Legal Issues of the Amsterdam Treaty (Hart, 1999).
[1] He was a member of the High Level Panel on the Free Movement of Workers established by the European Commission, chaired by Simone Veil.
[16][17][18][19] From 1990, in connection with the Enlargement of the European Union, particularly the accession of Central and Eastern European countries, he lectured on EU law and the legal consequences of EU accession on national law at universities and groups of civil servants, judges and legal practitioners particularly in Poland, Romania, Slovenia, Slovakia.