Andenæs is the UN Special Rapporteur on Arbitrary Detention, and the Chair of the UN Working Group on Arbitrary Detention which reports to the UN Human Rights Council and the UN General Assembly. He is a member of the Executive Council of the International Law Association.
He has held senior academic appointments in the United Kingdom, including as Director of the British Institute of International and Comparative Law, London and Director of the Centre of European Law at King’s College, University of London. He remains a Visiting Research Fellow of the Institute of European and Comparative Law, University of Oxford and a Senior Research Fellow at the Institute of Advanced Legal Studies, School of Advanced Studies, University of London.
He has been the General Editor of the International and Comparative Law Quarterly (Oxford University Press/Cambridge University Press).
He was the Secretary General of the Fédération internationale de droit européen 2000-2002, the Hon Secretary of the UK Association of European Law 1997-2008 and the Hon Secretary of the UK Committee of Comparative Law 1999-2005. He was the Chair, Association of Human Rights Institutes (AHRI) in 2008,
He was educated in Norway and England, and holds the degrees of Cand jur (Oslo), PhD (Cambridge) and MA and DPhil (Oxford).