• Permanent Mission of Mexico to the United Nations (map)
  • 2 United Nations Plaza
  • New York, NY

On the Interpretation and Application of Article 51 of the Charter

Side Event co-convened by the Permanent Missions of Mexico and Brazil to the United Nations

International Law Week 2026

Wednesday, 28 October 2026 | 8:15–9:45 a.m.

Permanent Mission of Mexico to the United Nations

2 United Nations Plaza, 28th Floor, New York

Background

Article 51 of the Charter of the United Nations recognizes the inherent right of individual and collective self-defence in case of an armed attack and establishes procedural elements concerning the exercise of that right, including the obligation to report measures taken in self-defence to the Security Council. The article also preserves the authority and responsibility of the Security Council with respect to the maintenance and restoration of international peace and security.

The interpretation and application of Article 51 have given rise to discussions on legal and institutional issues, including regarding the relationship between Article 2(4) and Article 51, the substantive and procedural aspects of the right of self-defence, and the role of the Security Council in relation to invocations of Article 51. As of mid-October, 169 letters referencing Article 51 have already been submitted in 2026 alone to the Security Council by 13 States, giving rise to the need to explore avenues to strengthen the legal and institutional framework underlying the exercise of the right of self-defence.

Against this background, the event will provide an opportunity for an open and technical exchange of views on recent developments in this area. The discussion will bring together perspectives from States, United Nations institutions, academia, and civil society, with a view to contributing to a broader understanding of the legal and institutional dimensions of Article 51.

Objectives

The event will seek to:

  • Exchange views on recent developments concerning the interpretation and application of Article 51 of the Charter.

  • Consider the relationship between Article 51 and the broader framework governing the nonuse of force under the Charter, including Article 2(4).

  • Discuss substantive and procedural aspects associated with invocations of Article 51, including questions of transparency and reporting to the Security Council.

  • Provide a presentation on the background information available to Member States regarding Article 51, including tools to access communications and reports.

  • Provide an opportunity to consider different State, institutional, academic, and civil society perspectives on the subject.

  • Present recent developments in the work of the Special Committee on the Charter, including Mexico’s proposal concerning the application of Article 51 and its interrelation with Article 2(4).

Panel

The event will bring together speakers representing different perspectives and areas of expertise, including:

  • Pablo Arrocha Olabuenaga, Legal Adviser, Ministry of Foreign Affairs of Mexico.

  • Prof. Naz K. Modirzadeh, Founding Director, Program on International Law and Armed Conflict, Harvard Law School.

  • Loraine Sievers, former Chief of the UN Security Council Secretariat Branch, and Coauthor of "The Procedure of the UN Security Council".

  • Maitê Schmitz, Legal Adviser, Permanent Mission of Brazil to the United Nations.

Ahead of the panel, Blanca Montejo, Senior Political Affairs Officer and Deputy Chief, Security Council Affairs Division, United Nations, will provide a brief presentation on the background information available to Member States in the Repertoire of the Practice of the Security Council as well as in the Peace and Security Datahub.