Chagos Archipelago sovereignty dispute

Did You Know?

• The Constitution of Mauritius states that the Republic of Mauritius includes the Chagos Archipelago, including Diego Garcia.
• The UN General Assembly resolution of 22 May 2019 demanded that the UK withdraw its colonial administration unconditionally within six months.

Historical background

Portuguese explorers charted the Chagos Archipelago as early as 1538, but no permanent settlement was established at that time. France progressively claimed and surveyed the archipelago in the mid-18th century, granting concessions for coconut plantations that led to permanent settlement. France administered the Chagos Archipelago as a dependency of the Île de France (Mauritius). In 1810, during the Napoleonic Wars, Britain took control of the Île de France and renamed it Mauritius. The 1814 Treaty of Paris formally ceded to the United Kingdom the territories that comprised the British Colony of Mauritius, including the Chagos Archipelago. From that date until 8 November 1965, when the archipelago was detached from the colony, it was administered by the UK as a Dependency of Mauritius. The economy was primarily driven by coconut plantations and copra exports, though other activities developed as the population expanded. British administration was exercised through visits by Special Commissioners and Magistrates from Mauritius.

Legal proceedings

On 20 December 2010, Mauritius initiated proceedings against the UK under the United Nations Convention on the Law of the Sea (UNCLOS), challenging the legality of the marine protected area (MPA) declared around the Chagos Archipelago in April 2010. Mauritius argued that Britain breached a UN resolution by separating Chagos from Mauritius before independence, and that the MPA was incompatible with Chagossian rights. The Permanent Court of Arbitration heard the dispute. Two arbitrators explicitly recognized Mauritian sovereignty; the other three found they lacked jurisdiction to rule on sovereignty. On 18 March 2015, the tribunal ruled the MPA illegal, determining that the UK's undertaking to return the archipelago gives Mauritius an interest in significant decisions about its future use.

2022–2025 negotiations

In November 2022, UK Foreign Secretary James Cleverly said the UK and Mauritius had agreed to negotiate a settlement based on international law, addressing issues like the former inhabitants and regional security, while ensuring the continued operation of the joint UK-US base on Diego Garcia. On 3 October 2024, a joint statement affirmed Mauritian sovereignty over the Chagos Archipelago, with the UK retaining control of Diego Garcia for 99 years. Later that month, Foreign Secretary David Lammy called the previous situation unsustainable, noting a binding legal ruling against the UK was unavoidable, making a negotiated deal the only way to keep the base running and comply with international law.

Reaction to 2025 agreement

The United States supported the deal. On 22 May 2025, Secretary of State Marco Rubio welcomed the historic agreement, confirming that the Trump administration had determined the long-term operation of the Diego Garcia base was secure, describing it as a critical asset for regional and global security. President Trump expressed his support for the achievement. On 23 May 2025, India welcomed the agreement as an important step in completing the decolonization of Mauritius. On 29 May 2025, a roundtable in Mauritius developed a program for a Mauritian delegation to travel to the Chagos Archipelago to raise the Mauritian flag, a symbolic step toward finalizing the restitution agreement. The majority of Chagossians live in Mauritius, with smaller communities in Seychelles and the United Kingdom. The Chagos Refugees Group in Mauritius, led by Olivier Bancoult, supported the agreement, considering Mauritian administration consistent with international legal rulings. The Chagos Community of Seychelles, led by Pierre Prosper, described the agreement as representing hope for eventual reinstallation and access to the islands.