Professor Seidl-Hohenveldern was born on 15 June 1918 in Mährisch-Schönberg, now Czech Republic. He studied law at the Universities of Vienna, Geneva and Innsbruck. In 1946 he started his career with the Liaison Services to the Allied Council for Austria in the Austrian Federal Chancellery and became Assistant Legal Advisor in the Constitutional Services of the Austrian Federal Chancellery in 1947. From 1949 to 1950 he served as Assistant Legal Advisor at the Organisation for European Economic Co-operation in Paris. From 1950 to 1954 he was Deputy Legal Advisor in the Foreign Affairs Department of the Austrian Federal Chancellery. In 1951 he became "Privatdozent" at the University of Vienna. This was the starting point of a most distinguished career in Public International Law. From 1954 to 1964 he was Professor of Public Law and Public International Law at the University of the Saar. In 1964 he moved to the University of Cologne. In 1981 he became Professor of Public International Law of the University of Vienna where he retired in 1988.

The oeuvre of Professor Seidl-Hohenveldern is very large and includes all areas of international law. His impressive list of publications encompass books and articles on general international law, international organisations, international economic law, international environmental law as well as European Community Law. It would be a to onerous task to discuss Professor Seidl-Hohenveldern's work in detail but it has been at the height of the discussion both concerning theory and practice. Indeed it would be difficult to find a topic to which he has not made a valuable contribution. This intensive work on international law problems has been acknowledged by the Hague Academy of International Law inviting Professor Seidl-Hohenveldern to lecture several times (1968 on The Impact of Public International Law on Conflict of Law Rules on Corporations, 1986 on International Economic Soft Law and in 1986 the general course on international law which he devoted to International Economic Law). His outstanding academic reputation has also been acknowledged by two "Festschriften" honouring Professor Seidl-Hohenveldern (Böckstiegel et al. (eds.), Law of Nations, Law of International Organisations, World's Economic Law (1988) and Hafner et al. (eds.), Liber Amicorum Professor Seidl-Hohenveldern (1998)).

Professor Seidl-Hohenveldern's commitment to international law has been acknowledged by a number of international and academic institutions. He was member of the Institut de droit international (since 1969) and Rapporteur of the International Law Association's Committee on Foreign Property and Nationalisation (1956 – 1960). From 1956 to 1974 he was Visiting Professor at the College of Europe, Bruges. Since 1974 he was Visiting Professor at the Europa Instituut of the University of Amsterdam. Furthermore, he was Corresponding Member of the Real Academia de Ciencias Morales and Politicas (since 1960), Member of the Austrian Academy of Sciences (since 1985) and of the Commssion médico-juridique de Monaco (since 1965). In 1978 he was awarded the honour of Docteur honoris causa de l'Université Paris V.  Seidl-Hohenveldern has also been a practitioner of international law. He has served, inter alia, as an arbitrator of the International Centre of the Settlement of International Investment Disputes and he was a member of the Special Panel of Adjudicators of the United Nations Relief and Work Agency and in several ad-hoc arbitrations. In 1983 he was President of the United Nations Conference on State Succession in respect of State Property, Archives and Debts.

The area of international economic, and in particular investment law, was particularly close to Ignaz Seidl-Hohenveldern. His post-graduate thesis (Habilitation) was an in-depth examination of nationalisations after WW I and WW II, within the context of the emergence of new states out of the Austrian empire, tensions between ethnic minorities and now majorities and, after WW II, Soviet occupation and introduction of Communism ( Internationales Konfiskations-und Enteignungsrecht (Tuebingen, 1952). The magisterial work on this tumultuous period of European history also reflects his own and his family's exposure to political risk and we may find here perhaps some personal explanation of the great respect Seidl-Hohenveldern had for private property and the link he always made between protection of property and personal liberties.  Many subsequent works – a comment on the Libyan oil nationalisations (RIW/AWD 1977, 522), his criticism of the assertion of unfettered nationalisation rights under the "NIEO" concept ( in:  Tomuschat (Ed), The UN At Age Fifty, A Legal Perspective, Kluwer, The Hague: 1995), a review of a book on valuation of compensation claims (Archiv des Voelkerrechts 32, June 1994 283), a comment on the investment protection regime of the Energy Charter Treaty (melanges Michael Waelbrook (ed. M. Dony), Bruylant, Bruxelles 1999) reflect his continuing involvement in the debate on the legitimate scope of state intervention into private property rights. The co-author had as far as 2001 an extended debate with Seidl-Hohenveldern about the question if mandatory third-party access (introduced under modern EU energy directives and national implementing law) was a compensable "taking" (Seidl-Hohenveldern naturally argued so with great vigour). Any request made to this distinguished scholar with a massive memory and library was responded to in full: a recent query about confiscatory taxation produced cases and writings from the 1920 to the 1990s. His great work, in the field of international economic law, is his Kluwer-published "International Economic Law" (third edition, 1999, reviewed by the co-author in 2 JWI (2001), with a review of the second edition in: 11 JENRL (1993) 326-327). It provides a running commentary on most of the economic law disputes that have challenged international lawyers throughout the last 50 years. It provides – different from the much more one-dimensional works one now gets on international economic law – a complex, historically rich and always sceptical perspective on these vexing questions using thoughts from the great diversity of legal cultures;  Seidl-Hohenveldern was at ease with legal writing in English, German, French, Spanish and Italian and engaged in friendly debates with colleagues throughout the world. The two authors of this note are personally grateful to a scholar and mentor who for decades has been a constant friend, supporter (and a living bibliography of rare cases and arguments).