In Vienna, on 21 March 1986, the Vienna Convention on the Law of Treaties Between States and International Organizations or Between International Organizations (VCLTIO) opens for signature. The depositary is the UN Secretary-General; the authentic languages are Arabic, Chinese, English, French, Russian and Spanish.

The instrument extends the 1969 Vienna Convention on the Law of Treaties (VCLT), which covers only treaties between States. The International Law Commission drafted the text to regulate the conclusion, application, interpretation and termination of treaties to which at least one party is an international organization.

Article 85 requires ratification or accession by 35 States for entry into force. At documentation, 34 States and several organizations (formal confirmations by the UN, ILO, WHO, ICAO, IAEA and others) are parties or have confirmed, but the 35-State threshold is unmet — the Convention is not yet in force.

State parties include Mexico, Argentina, Australia, the United Kingdom, Germany, Italy, the Netherlands, Brazil and Palestine. Non-ratifying signatories include the United States, Japan and Egypt. Organizations that signed without completed formal confirmation include the Council of Europe, FAO and UNESCO.

Even while not in force, VCLTIO is cited as a codification of customary rules on organizations’ treaty-making capacity and as guidance for secretariat practice.

The Vienna Convention of 21 March 1986 remains the key instrument that complements the 1969 VCLT for treaties involving international organizations, still awaiting the thirty-fifth State ratification.

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

Source consulted: Vienna Convention on the Law of Treaties Between States and International Organizations. Treaty text: Vienna Convention on the Law of Treaties between States and International Organizations (UNTC XXIII-3).