Member of the International Law Commission of the United Nations from 1986 to 1996. Special Rapporteur on State Responsibility from 1987 to 1996.
Member of the Board of Directors of the Rivista di Diritto Internazionale.
Professor of International Law in the Universities of Camerino, Padova, Bologna and Rome (“La Sapienza”). In the latter University, Emeritus of International Law.
Professoral Courses at the Hague Academy of International Law in the years 1962, 1972, 1979 and 1984 (general course of public international law).
Visiting professor at the Hague Law School of the University of Virginia (1965).
Member of the International Law Institute.
Docteur Honoris Causa Université Panthéon – Assas, Paris (1997).