VCLT 1986

The Vienna Convention on the Law of Treaties between States and International Organizations or between International Organizations was adopted in Vienna on 21 March 1986. It complements the earlier 1969 Vienna Convention on the Law of Treaties (VCLT 1969), which applies only to treaties concluded between states. The 1986 instrument extends substantively identical rules to treaties where at least one party is an international organization, such as the United Nations, the European Union, or the World Health Organization.

The Convention was drafted by the International Law Commission (ILC), with Special Rapporteur Paul Reuter producing successive draft articles between 1972 and 1982. It was negotiated at a UN conference in Vienna in February–March 1986 and opened for signature on the day of adoption.

Key features track the 1969 VCLT closely:

• Capacity to conclude treaties is recognized for international organizations, but governed by the rules of each organization (Article 6).
• Consent to be bound, reservations, entry into force, interpretation, invalidity, termination, and suspension follow the architecture of the 1969 text, adapted for organizational parties.
• Pacta sunt servanda (Article 26) and the rule against invoking internal rules to justify non-performance (Article 27) apply, with a specific clause on the rules of the organization.
• Jus cogens (Articles 53 and 64) is preserved as a ground for invalidity and termination.

As of the mid-2020s, the Convention has not yet entered into force, because it requires 35 ratifications by states (international organizations may also become parties, but their instruments do not count toward the 35 threshold under Article 85). Despite this, many of its provisions are widely regarded as reflecting customary international law and are routinely cited by the International Court of Justice, arbitral tribunals, and treaty bodies when organizations are involved.