Extends international treaty law to cover agreements involving international organizations, though it has not yet entered into force due to insufficient ratifications.
Key Facts
- Opened for signature
- 21 March 1986
- Ratifications required
- 35 states
- Ratifications as of June 2025
- 33 states
- Current status
- Not yet in force
- Developed by
- International Law Commission
By the Numbers
Location
Cause → Event → Consequence
The 1969 Vienna Convention on the Law of Treaties governed treaty-making between states but did not address the growing role of international organizations as treaty parties. The International Law Commission identified this gap and undertook work to extend treaty law principles to cover organizations such as the United Nations and its specialized agencies.
The Vienna Convention on the Law of Treaties Between States and International Organizations or Between International Organizations (VCLTIO) was opened for signature on 21 March 1986. Developed by the International Law Commission, it extends the framework of the 1969 Vienna Convention to treaties in which one or more parties are international organizations rather than sovereign states.
Despite being opened for signature in 1986, the VCLTIO has not entered into force, as it requires ratification or accession by 35 states and had reached only 33 as of June 2025. Nevertheless, many of its provisions are widely regarded as reflecting customary international law and are applied in practice by states and international organizations.
Political Outcome
Convention opened for signature but has not entered into force, lacking the required 35 ratifications as of June 2025.