---
title: "Chagos Advisory Opinion: 2019 ICJ Ruling | Model Diplomat"
description: "The Chagos Advisory Opinion is the ICJ's 2019 finding that the UK unlawfully detached the archipelago from Mauritius, obliging it to end its administration."
url: "https://modeldiplomat.com/learn/glossary/chagos-advisory-opinion"
---

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Model Diplomat Research Team · Last reviewed June 22, 2026

TL;DR

- The Chagos Advisory Opinion is the 2019 International Court of Justice ruling that the United Kingdom's detachment of the Chagos Archipelago from Mauritius before independence rendered decolonization unlawful.
- Is the Chagos Advisory Opinion legally binding on the United Kingdom?
- Why did the ICJ reject the UK's argument that this was a bilateral dispute?
- What did the opinion say about the right of self-determination?
- How does the opinion affect the Chagossians who were displaced?

Updated June 22, 2026

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## Timeline

1. 25 February 2019

   The Chagos Advisory Opinion, formally titled Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, was delivered by the Inte…

2. 22 June 2017

   The request originated in General Assembly Resolution 71/292, adopted on by a vote of 94 to 15, which posed two questions: whether the decolonization of Mau…

3. 14 December 1960

   It anchored this in General Assembly Resolution 1514 (XV) of , the Declaration on the Granting of Independence to Colonial Countries and Peoples, which it tr…

4. 22 May 2019

   The General Assembly endorsed it through Resolution 73/295 on , by 116 votes to 6, demanding UK withdrawal within six months.

5. 3 October 2024

   Diplomatic pressure culminated in negotiations between London and Port Louis, and on the UK announced an agreement to transfer sovereignty over the Chagos A…

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Example

In its 25 February 2019 opinion, the International Court of Justice held by thirteen votes to one that the United Kingdom must end its administration of the Chagos Archipelago, prompting Mauritius to press its sovereignty claim at the UN General Assembly.

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