On 23 August 1978, in Vienna, the Vienna Convention on Succession of States in Respect of Treaties is concluded — the UN instrument codifying rules on the effects of state succession on bilateral and multilateral treaties.

The Convention was adopted by the UN Conference on Succession of States (second session, 31 July–23 August 1978) and opened for signature from 23 August 1978. It distinguishes “newly independent states” (former colonies) from other cases of territorial separation.

Article 16 provides that newly independent states do not automatically inherit the colonial power’s treaty obligations (clean slate), whereas article 34 generally maintains treaty links for other new states. Entry into force came on 6 November 1996 (15 parties).

The depositary is the UN Secretary-General; authentic texts are Arabic, Chinese, English, French, Russian and Spanish (UNTS vol. 1946).

For the international law of treaties, 23 August 1978 marks the Convention’s conclusion.

The full text is published by the International Law Commission / UN.

The Vienna Convention on Succession of States in Respect of Treaties of 23 August 1978 remains the legal decolonisation milestone.

Image: Vienna; Wikimedia Commons. Cropped to 16:9.

Source consulted: Vienna Convention on Succession of States in Respect of Treaties. Treaty text: UN ILC — Vienna Convention (succession, 1978).