Depositary Functions in Diplomacy

Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

The administrative duties performed by a state or international organization entrusted with the custody and management of a treaty's authentic text and related instruments.
Can a depositary refuse to accept a reservation?
Who is the most common depositary for multilateral treaties?

Updated June 22, 2026

The administrative duties performed by a state or international organization entrusted with the custody and management of a treaty's authentic text and related instruments.

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Example

When Palestine deposited its instrument of accession to the Rome Statute with the UN Secretary-General in January 2015, the Secretary-General acted in his depositary capacity by circulating notification C.N.13.2015.TREATIES-XVIII.10 to all states parties.

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Depositary functions are the formal custodial and administrative tasks carried out by the entity designated in a treaty to safeguard its authentic text and to service the treaty regime over time. The role is codified in Articles 76–80 of the 1969 Vienna Convention on the Law of Treaties (VCLT), which set out both who may be a depositary and what the depositary does.

A depositary may be one or more states, an international organization, or the chief administrative officer of such an organization (VCLT Art. 76). The UN Secretary-General is the depositary for over 560 multilateral treaties deposited with the United Nations, while other common depositaries include the Swiss Federal Council (Geneva Conventions), the OAS Secretary-General, and the Council of Europe.

Core functions under VCLT Article 77 include:

Keeping custody of the original text and any full powers delivered to the depositary.
Preparing certified copies and additional languages required by the treaty.
Receiving signatures, instruments of ratification, acceptance, approval, or accession, and reservations or objections.
Examining whether such instruments are in due and proper form.
Informing parties and signatories of acts, notifications, and communications relating to the treaty.
Registering the treaty with the UN Secretariat under Article 102 of the UN Charter.
Notifying entry into force once the required threshold of consent is met.

The depositary's role is impartial and ministerial, not adjudicative. Under VCLT Art. 77(2), if a question arises about the performance of its functions, the depositary must bring the matter to the attention of the signatory states or, where appropriate, the competent organ of the relevant international organization, rather than decide it unilaterally.

Frequently asked questions

Can a depositary refuse to accept a reservation?

No. Under VCLT Article 77(2), the depositary's role is ministerial; it circulates the reservation to other states and lets them decide whether to object.

Who is the most common depositary for multilateral treaties?

The UN Secretary-General, who currently serves as depositary for more than 560 multilateral treaties, including most major human rights and disarmament instruments.