The VCLT established binding international rules for how treaties between states are drafted, interpreted, and enforced, serving as the primary authority in treaty law.
Key Facts
- Adopted & opened for signature
- 23 May 1969
- Entered into force
- 27 January 1980
- Ratifying states (as of Feb 2026)
- 118 sovereign states
- Common name
- Treaty on treaties
- Scope
- Governs treaties between sovereign states only
By the Numbers
Location
Cause → Event → Consequence
Before the VCLT, the rules governing how international treaties were concluded, interpreted, and terminated relied largely on fragmented customary international law and state practice, creating inconsistency and disputes. The international community sought a codified, authoritative framework to standardize treaty relations among sovereign states.
On 23 May 1969, the Vienna Convention on the Law of Treaties was adopted and opened for signature. It defined treaties as written international agreements between states governed by international law, and set out rules covering their drafting, amendment, interpretation, invalidity, and termination.
The VCLT entered into force on 27 January 1980 and became the foundational authority in international treaty law, ratified by 118 states. Even non-ratifying states such as the United States have recognized significant portions of the VCLT as reflecting binding customary international law, broadening its practical reach beyond formal ratification.
Political Outcome
The Convention entered into force on 27 January 1980 and has been ratified by 118 sovereign states, establishing the authoritative legal framework for international treaty relations.
Treaty relations governed by fragmented customary international law and inconsistent state practice
Unified codified framework under VCLT as the primary authority for treaty interpretation and dispute resolution