The Office of Legal Affairs (OLA) is the central legal arm of the United Nations Secretariat, established to provide unified legal services across the organization. Its existence traces to the original Secretariat structure approved by the General Assembly in 1946, and it operates today under the authority of the Secretary-General as delineated by Article 97 of the UN Charter and successive Secretary-General bulletins on the organization of the Secretariat (most recently ST/SGB/2008/13, which sets out OLA's mandate, structure, and reporting lines). The head of OLA, designated the Under-Secretary-General for Legal Affairs and United Nations Legal Counsel, ranks among the senior-most officials of the Secretariat and serves as the principal legal adviser to the Secretary-General on questions of public international law, UN internal law, and the law of the host country relationships.
Procedurally, OLA's work begins when a request for legal advice or service is transmitted from a principal organ, a Secretariat department, a peacekeeping operation, a specialized agency, or a member-state mission. Requests are routed to the appropriate division, which prepares a written legal opinion, drafts treaty or contractual language, or represents the Organization in proceedings. Formal legal opinions of the Legal Counsel are published in the United Nations Juridical Yearbook and are treated as authoritative statements of the Secretariat's legal position. When a member state submits an instrument of ratification or accession to a multilateral treaty deposited with the Secretary-General, OLA's Treaty Section examines the instrument for conformity with depositary practice, registers reservations and declarations, and circulates a depositary notification (C.N.) to all states concerned.
OLA is organized into six divisions, each with distinct competence. The Office of the Legal Counsel handles constitutional and high-political questions, including privileges and immunities under the 1946 Convention on the Privileges and Immunities of the United Nations. The General Legal Division advises on contracts, claims, and administrative-tribunal litigation. The Codification Division services the International Law Commission and the Sixth Committee of the General Assembly. The Division for Ocean Affairs and the Law of the Sea (DOALOS) services the institutions established under the 1982 UN Convention on the Law of the Sea. The International Trade Law Division serves as secretariat to UNCITRAL. The Treaty Section discharges the Secretary-General's depositary functions for over 560 multilateral treaties pursuant to Article 102 of the Charter, which requires registration of every treaty entered into by a UN member.
In recent practice, OLA's Legal Counsel has issued opinions of considerable consequence. Miguel de Serpa Soares of Portugal served as Under-Secretary-General for Legal Affairs from 2013 until 2024, when he was succeeded by Elinor Hammarskjöld of Sweden, appointed by Secretary-General António Guterres. During the Russian invasion of Ukraine, OLA advised on the legal status of credentials challenges and on sanctions implementation by Secretariat entities. OLA was also instrumental in negotiating the 2022 Black Sea Grain Initiative concluded in Istanbul, drafting the headquarters agreement for the Joint Coordination Centre. The Office has likewise managed depositary functions for the 2017 Treaty on the Prohibition of Nuclear Weapons and the 2023 Agreement under UNCLOS on Biodiversity Beyond National Jurisdiction (BBNJ Agreement).
OLA must be distinguished from the International Court of Justice (ICJ), which is the principal judicial organ of the UN under Charter Chapter XIV and operates independently from the Secretariat. OLA neither litigates before the ICJ on behalf of member states nor adjudicates disputes; it may, however, transmit requests for advisory opinions from authorized UN organs and present the Secretary-General's views in written and oral proceedings, as it did in the 2024 advisory proceedings on Israeli practices in the Occupied Palestinian Territory. OLA is also distinct from the Office of Administration of Justice, which manages the UN Dispute Tribunal and Appeals Tribunal, and from in-house counsel offices of specialized agencies such as WHO or UNESCO, which maintain their own legal services under separate constituent instruments.
Controversies surrounding OLA have centered on its dual role as adviser to the Organization and as guardian of UN legal positions vis-à-vis member states. The 2004 Volcker Inquiry into the Oil-for-Food Programme criticized aspects of OLA's contracting advice. More recently, OLA's interpretation of the Convention on the Privileges and Immunities of the UN was tested in the cholera litigation arising from the 2010 Haiti epidemic, where OLA invoked absolute immunity, a position upheld by the U.S. Second Circuit in Georges v. United Nations (2016) but criticized by human-rights commentators. OLA has also navigated the increasingly contested terrain of host-country obligations, including U.S. visa denials to delegations attending headquarters meetings, which OLA has formally protested as inconsistent with Section 11 of the 1947 UN Headquarters Agreement.
For the working practitioner, OLA is the indispensable interlocutor on any matter touching the legal personality, privileges, or treaty commitments of the United Nations. Desk officers preparing instruments of ratification consult the Treaty Section's online United Nations Treaty Collection and its Final Clauses Handbook for drafting guidance; legal advisers in foreign ministries rely on OLA depositary notifications to track entry-into-force thresholds; and counsel for troop-contributing countries engage the Office of the Legal Counsel on status-of-forces questions. Mastery of OLA's procedures—how to file a reservation, how to request a legal opinion through one's Permanent Mission, how to register a bilateral treaty under Article 102—is a baseline professional competence for any diplomat operating in the multilateral system.
Example
In September 2023, the UN Office of Legal Affairs Treaty Section opened the BBNJ Agreement for signature at UN Headquarters in New York, receiving 67 signatures on the first day.