"Vienna Convention on State Succession" actually refers to two separate instruments produced by the International Law Commission and adopted at UN conferences in Vienna:
- The Vienna Convention on Succession of States in Respect of Treaties (adopted 23 August 1978, entered into force 6 November 1996).
- The Vienna Convention on Succession of States in Respect of State Property, Archives and Debts (adopted 8 April 1983, not yet in force).
Both regulate the legal consequences when sovereignty over territory changes — through decolonization, unification, separation, dissolution, or transfer of territory. The 1978 Convention sets default rules on whether successor states inherit the treaty obligations of their predecessor. It distinguishes newly independent states (former colonies), which benefit from a "clean slate" rule allowing them to choose which multilateral treaties to continue, from cases of separation or dissolution, where treaties in force generally continue automatically for the successor (the principle of continuity). Boundary regimes and other territorial treaties always pass to the successor under Article 11.
The 1983 Convention addresses the division of state property located in the transferred territory, the allocation of archives, and the apportionment of state debts, again with more protective rules for newly independent states.
Ratification has been limited. The 1978 Convention has roughly two dozen parties, mostly post-Soviet, post-Yugoslav, and post-colonial states; the 1983 Convention has never reached the 15 ratifications needed to enter into force. As a result, much practice on state succession is governed by customary international law and by ad hoc agreements — for example, the 2001 Agreement on Succession Issues among the former Yugoslav republics, or the bilateral arrangements following the 1993 dissolution of Czechoslovakia and the 1991 dissolution of the USSR (in which the Russian Federation was accepted as the continuator state, including at the UN Security Council).
The Conventions remain influential as authoritative codifications, frequently cited by the ICJ and arbitral tribunals even against non-parties.
Example
When South Sudan seceded from Sudan in July 2011, the two states negotiated bilateral arrangements on oil revenues, debt, and treaty continuity that drew on principles reflected in the 1978 and 1983 Vienna Conventions.
Frequently asked questions
The 1978 treaties convention entered into force in 1996 with limited ratifications. The 1983 convention on property, archives, and debts has not entered into force.
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