He holds a J.D. from Harvard Law School, a PhD in Modern history from University of Göttingen and a B.A. in philosophy and history from Fordham University. A member of the New York and Florida Bars, he practised law in the law firm Simpson Thatcher and Bartlett in New York for three years, and then moved to Europe with a Fulbright Graduate Fellowship. He was head of an “Arbeitsgruppe Kriegsvölkerrecht” (workshop on international humanitarian law) at the University of Göttingen, a senior fellow at the Max Planck Institute in Heidelberg and member of the editorial committee of the Encyclopedia of Public International Law. He has received many honors including the 2011 Educators Award of Canadians for Genocide Education. In 2012, he was appointed UN Independent Expert on the promotion of a democratic and equitable international order by the UN Human Rights Council.
In January 1981 he became a staff member of the then UN Division of Human Rights in Geneva, and worked for 22 years as a lawyer for the United Nations, taking early retirement in 2003 in order to teach and write. He was Secretary of the United Nations Human Rights Committee, Senior Human Rights Officer, Deputy Chief of the Communications Branch and Chief of the Petitions Section.
He has been Visiting Professor of International Law at DePaul University (Chicago), the Human Rights Centre at Galway (Ireland), the University of British Columbia in Vancouver (Canada), the Universität Trier (Germany), the Schiller International University in Leysin (Switzerland), the Raoul Wallenberg Institute at the University of Lund (Sweden), the Universidad de Alcalá de Henares in Madrid (Spain), the Académie internationale de droit constitutionnel (Tunis), the Santa Clara Law School at Geneva , the Belgrade Centre for Human Rights, the Institute of Humanitarian Law at San Remo, the Institut des Droits de l’Homme at Strasbourg, and the Graduate Institute of the University of Geneva (Switzerland).
He regularly participates in UN panels and expert groups, including the UN workshop on “The human right to peace “, (Report of the Office of the High Commissioner on the outcome of the experts workshops on the right of peoples to peace)
He was President of the UN Society of Writers 1990-2005 and remains Editor-in-Chief of the UN literary journal “Ex Tempore”, which has issued 22 volumes. For many years Secretary-General of PEN International, Centre Suisse Romande, he was elected President in 2006.
- Public International Law
- International Humanitarian Law
- International Jurisprudence
- Human Rights
- World History
- Nemesis at Potsdam: (first edition, Routledge, London and Boston 1977) 6th revised edition, Picton Press, Rockland, Maine, 2003 296 pp. 14th enlarged German version: Die Nemesis von Potsdam. Die Anglo Amerikaner und die Vertreibung der Deutschen (First edition 1977, C.H.Beck, Munich; 14th revised edition, 2005, Herbig Verlag, Munich) 416 pages.
- The Wehrmacht War Crimes Bureau 1939 1945: (first edition 1989, University of Nebraska Press; fourth revised edition, Picton Press, 2000). Original German version: Die Wehrmacht Untersuchungsstelle (1st edition 1979, 7th revised and enlarged edition, 2001, Universitas/Langen Müller, Munich), 510 pages. Excerpts reprinted in Marco Sassoli and Antoine Bouvier, How does law Protect in War? Cases and Materials on International Humanitarian law in Contemporary Practice, International Committee of the Red Cross, Geneva, 1999.
- The German Expellees: Victims in War and Peace, Macmillan, London, 1993. Revised and enlarged paperback version, published under the title: A Terrible Revenge: The Ethnic Cleansing of the East-European Germans 1944-1950 (4th revised edition Palgrave/Macmillan 2006). Original German version: Anmerkungen zur Vertreibung (4th revised edition, 1995), Kohlhammer, Stuttgart, 240 pp., 5th revised edition 2005, Leopold Stocker Verlag, Graz.
- Heimatrecht ist Menschenrecht (Universitas/Langen Müller, Munich, 2001) 296 pp.
- 50 Thesen zur Vertreibung. Verlag Inspiration, München 2008.
- The Genocide against the Armenians and the Relevance of the 1948 Genocide Convention, Haigazian University Press, Beirut, 2010.
- Völkermord als Staatsgeheimnis, Olzog Verlag, Munich 2011.
- Co-author with Judge Jakob Th. Möller of the Handbook: United Nations Human Rights Committee Case-Law 1977-2008, N.P. Engel Verlag, Kehl/Strasbourg, 2009. Review on Human Rights Quartely Journal – February 2010, Volume 32, number 1. Pag 237-240
- Co-author and co-editor with Gudmundur Alfredsson and Bertrand Ramcharan of International Human Rights Monitoring Mechanisms, Brill, Amsterdam 2009.
- Author of 18 entries in Rudolf Bernhardt (ed.) Encyclopedia of Public International Law, North Holland Publishers, Amsterdam 1990-2003.
- Author of 6 entries in David Forsythe (ed) Encyclopedia of Human Rights, Oxford 2009
- Author of 6 entries in Rüdiger Wolfrum (ed.) Max Planck Encyclopedia of Public Inernational Law, Oxford 2009
- Author of 4 entries in Dinah Sehlton (ed.), Encyclopedia of Genocide, Macmillan Reference, 2005
- Author of the entry on “United Nations High Commissioner for Human Rights” in Helmut Volger, Concise Encyclopedia of the United Nations”, Brill, 2009.