Chagos Islands deal shelved – legal expert explains what happens next
The UK government has shelved legislation to return the Chagos Islands to Mauritius, after the US government withdrew its support for the deal.
Until and unless the US gives their consent, the UK will not be able to pass legislation, and the treaty between the UK and Mauritius to transfer sovereignty, signed in 2025, cannot be put into effect. This is because the agreement would require a 1966 British-American treaty on the Chagos Islands to be amended. Formal letters needed to be exchanged for this to happen, and the US will not provide theirs.
The US president, Donald Trump, has changed his mind on the issue several times. While initially granting support for the deal, in January 2026, he called it an “act of great stupidity”. In February 2026, Trump told the UK on social media: “DO NOT GIVE AWAY DIEGO GARCIA!”, saying that the US might want the US-UK military base on Diego Garcia to be used in operations against Iran.
Under the deal, Mauritius would allow the US and UK to access, maintain, and invest in the base for an initial 99-year period, which can be extended if both parties agree. In exchange, the UK will pay Mauritius an annual average of £101 million for 99 years in 2025-26 prices, totalling around £3.4 billion.
In the UK, there has been opposition to the deal from the Conservatives. Their leader, Kemi Badenoch, argued that the payments to Mauritius are unacceptable, and questioned Mauritius’s ties to China, claiming UK national security is being put at risk. This opposition is despite the fact the previous Conservative government started negotiating the treaty with Mauritius. Reform UK leader Nigel Farage has claimed that there is no legal basis for the deal.
Sovereignty over the Chagos Islands has been disputed since the UK detached them from the colony of Mauritius in 1965, before Mauritius gained independence in 1968. A treaty between the UK and US in 1966 allowed the US to lease Diego Garcia for a joint military base on British territory, in exchange for which the US reportedly gave the UK a discount on nuclear weapons technology. This treaty was based on the UK having sovereignty over the Chagos Islands, so –under the proposed deal – it would need amending to state that the US is leasing the military base’s land from Mauritius, rather than the UK.
The Chagossians were removed from their homeland to make way for the airbase. The rights of the Chagossians and their descendants (who were British subjects) were removed by the UK government.
Following a decades-long campaign, several international court decisions in recent years have held that this action was illegal, and Mauritius should have sovereignty over the Chagos Islands. This pressure led to the negotiation of the 2025 treaty between the UK and Mauritius.
To give domestic legal force to the new treaty, legislation would have to be passed. This was the Diego Garcia Military Base and British Indian Ocean Territory bill, which had nearly passed all its parliamentary stages. But the UK government has run out of time to pass it in this parliamentary session, and there are no plans to introduce a new bill next parliament. In effect, the deal is dead.
The UK is now in a difficult position. It retains sovereignty over the Chagos Islands, but there remain several international law judgments declaring that the UK must return the islands to Mauritius, to complete the decolonisation process.
The UK is committing a serious and ongoing violation of international law by retaining sovereignty. Countries that commit such violations can be ostracised by the international community. For example, Turkey’s application to join the European Union has stalled in part due to its support for the breakaway (and unrecognised) Northern Cypriot Republic.
There is also now further uncertainty over the future of the Chagossians. Under the UK-Mauritius treaty, the Chagossians would have had a right to return to some of the Chagos Islands, save for Diego Garcia. The UK has historically banned the return of the Chagossians to all of the islands.
International pressure
Mauritius has now announced that it will continue to pursue its claim to sovereignty. Dhananjay Ramful, the Mauritian foreign minister, told an Indian Ocean conference in Mauritius that his government would regain control over the territory, saying: “We will spare no effort to seize any diplomatic or legal avenue to complete the decolonisation process”.
Mauritius is likely to pursue its case through the United Nations, as it has done in recent years. This could lead to the International Court of Justice being asked to rule again on the legality of the UK’s actions. While ICJ judgments are not binding, they have political force.
The Chagossian community has led a longstanding legal and political campaign to return to their homeland. Many Chagossians have wanted a say in the future of the land they were exiled from, and have tried to achieve this through legal routes. On March 31 2026, they succeeded in a legal challenge at the British Indian Ocean Territory Supreme Court (equivalent to the English High Court). The ruling overturned a 2004 law which denied the Chagossians a right of abode in the Chagos Islands.
Mauritius is also a member of the Commonwealth of Nations, and has close relations with other Commonwealth countries such as India. Mauritius also has good relations with France, a member of the European Union. This could enable them to lobby their allies to place further pressure on the UK through vehicles like trade deals, requesting a handover of the Chagos Islands as a price for signing treaties and agreements with the UK.
Given Trump’s recent criticisms of Keir Starmer over the perceived failure in UK support over the Iran war, we should not expect the US to agree to the Chagos handover in the foreseeable future. This could mean further pressure on the UK at the UN and other international bodies, and difficulties for the UK’s international standing. The US may be powerful enough to ignore international law with few short-term consequences, but the UK is not.
Tom Frost receives funding from the Socio-Legal Studies Association, designed to pursue research into the ongoing influence of the British Empire on the UK's constitution.