Full Professor of European and public law, Jean-Monnet-Professor of European Law, Head of the Department of European Law at the Faculty of Law and Administration of the Jagiellonian University in Kraków (1994-2018).
For nearly 15 years, he taught at the National School of Public Administration in Warsaw. He was a member of the Legislative Council at the Office of the Prime Minister and subsequently became a judge of the Supreme Administrative Court (2001-2008) and the Constitutional Tribunal (2008-2017), where he also served as Vice-President (2010-2017). He is a member of many Polish and international scientific organizations, inter alia: member and vice-president of the Legal Sciences Commitee of the Polish Academy of Sciences, member of the Legal and European Committees of the Polish Academy of Learning, a co-founder and first president of the Polish Association of European Law (a branch of FIDE), member and a member of the board (2010-2013) of SIPE (Societas Iuris Publici Europae), and a member of the European Network of European Law.
He has authored and edited well over 100 publications (books, articles, court commentaries) mostly in Polish, English and German. He received scholarships to research abroad in the USA (University of Wisconsin), United Kingdom (All Souls College, Oxford) and Germany (including a scholarship of the Alexander von Humboldt Foundation in Heidelberg, Wissenschaftskolleg zu Berlin), among others. He is a doctor honoris causa of the Friedrich-Schiller-Universität in Jena.
He has delivered numerous lectures and papers in Poland, in many European countries (Austria, Germany, United Kingdom, France, Netherlands, Sweden, Norway, Finland, Ireland, Lithuania, Latvia, Czech Republic, Romania, Bulgaria, Greece, Italy, Spain, Portugal, Ukraine), as well as outside of Europe (USA, Canada)
Editor-in-chief of the "European Judiciary Review".