50 Years Vienna Convention on the Law of Treaties

The Conference “50 Years Vienna Convention on the Law of Treaties (VCLT)”, organised by August Reinisch and Christina Binder on the occasion of Prof. Zemanek’s 90th birthday on 18 November 2019, assembled more than 120 participants from all over the world; academics as well as practitioners.

The Conference took the VCLT’s anniversary as a starting point to examine the law of treaties over the past five decades. Panels, consisting of Hanspeter Neuhold, Veronika Bílková, Georg Nolte, Catherine Brölmann, Gerhard Hafner, Christina Binder, Hélène Ruiz Fabri, and Dire Tladi, examined the historical origins of the VCLT; developments in the law of treaties over the last 50 years, including the interpretation of treaties, subsequent practice in relation to treaties, reservations, the provisional application of treaties and treaty termination. A final panel dealt with the “eternal question of ius cogens.”

Indeed, the Vienna Convention on the Law of Treaties (VCLT), negotiated and adopted in Vienna in 1969, is frequently called the “treaty of treaties”. The VCLT is the most important instrument of modern treaty law, with the vast majority of its provisions codifying customary international law. State and judicial practice are continuously guided by the authoritative rules incorporated in the VCLT. At the same time, the VCLT’s general rules were further developed and modified by subsequent practice as well as by developments especially in specific treaty regimes. All this was discussed at the conference’s stock-taking in the year of the 50th birthday of the VCLT.