UK-Mauritius Chagos sovereignty deal stalls amid fears of further delays

Pointe aux Sables, Mauritius – “At one funeral, we scattered sand from Chagos into an elder’s tomb to honour his unfulfilled wish to breathe his last in his homeland,” says Olivier Bancoult of the Chagos Refugees Group.

For elderly Chagossians displaced from their Indian Ocean homeland decades ago, delays to a treaty allowing their return are raising fears that they may never see the islands again.

The agreement, signed by Britain and Mauritius in May 2025, would allow resettlement on islands other than Diego Garcia, which would remain a military base. But it has yet to enter into force amid opposition from US President Donald Trump.

“We remain unshaken by Trump’s interference in the Chagos deal,” Bancoult says.

“The 2019 ICJ advisory opinion in favour of the archipelago’s return to Mauritius has restored our dignity and faith in our rights as native Chagossians.”

The Chagos archipelago, a group of islands in the Indian Ocean, was separated from Mauritius by Britain in 1965, three years before Mauritius gained independence. Britain later established a military base with the US on Diego Garcia, the largest island in the group.

Between 1968 and 1973, Britain removed an estimated 1,400 to 1,700 Chagossians from the islands. Many were resettled in Mauritius and the Seychelles, with others later moving to the United Kingdom. British authorities also made it illegal to remain on or return to the islands without permission.

“If Trump wants to meddle in this matter, well, let him,” Bancoult says. “We’ve had the 2019 ICJ [International Court of Justice] advisory opinion, the International Tribunal for the Law of the Sea’s 2021 judgement, and the 2025 UK-Mauritius treaty providing for Mauritius to exercise sovereignty over the archipelago. International law is squarely on our side.”

Signed on May 22, 2025, the treaty provides for Mauritius to exercise sovereignty over the Chagos archipelago, while allowing the UK to exercise rights over the Diego Garcia military base for an initial 99-year period. It also allows Mauritius to arrange for the resettlement of Chagossians on islands other than Diego Garcia. The treaty has not yet entered into force.

In April, the UK government told Parliament that the legislation needed to implement the agreement could not complete its passage during the 2024–26 parliamentary session. The session ended on April 29, meaning the bill made no further progress.

In January, Trump criticised the agreement, calling it an “act of great stupidity ” and questioning whether it adequately protected the Diego Garcia military base.

The issue returned to the diplomatic agenda in September. On September 21, British Prime Minister Andy Burnham said the UK would work with Mauritius and the US on a way forward that secures the operation of Diego Garcia and protects UK national security.

On September 26, Mauritian Prime Minister Navin Ramgoolam travelled to the UK for talks with British National Security Adviser Jonathan Powell and other officials on the Chagos issue. He remains in London, with the Mauritian government saying the discussions would cover recent developments concerning the archipelago.

For Bancoult, the central question is whether elderly Chagossians will live long enough to see the treaty’s promises fulfilled.

“Chagossians born on the archipelago are now aged between 58 and 100. We are growing old, and we have lost several Chagossian elders this year alone,” he says.

For younger Chagossians, the consequences are also cultural.

Chrisyl Wong-Hang-Sun, a PhD researcher in anthropology at the University of Edinburgh, says years of displacement and migration are making it harder to preserve Chagossian culture.

“During my fieldwork, many diaspora members expressed concerns over cultural loss, such as words in Chagossian Creole and recipes that are difficult to recreate abroad,” she says. “Descendants of Chagossians, myself included, long to know the islands of their relatives and ancestors.”

The dispute has also exposed political differences among Chagossians.

“The actions of both the British and Mauritian governments have resulted in very nuanced and differing political opinions among Chagossians across the UK, Mauritius and the Seychelles,” Wong-Hang-Sun says.

The Chagos Refugees Group is at odds with UK-based second-generation Chagossian Misley Mandarin and his supporters, who favour resettlement under British rather than Mauritian sovereignty and have received backing from Reform UK.

Wong-Hang-Sun says those differences should be recognised as negotiations continue.

Both governments, she says, need to “find ways to prioritise and engage with the Chagossian diaspora as a whole”.

Mauritius keeps talks largely private

Mauritius has disclosed little publicly about the substance of the latest talks on Chagos.

At the United Nations General Assembly in September, Foreign Minister Dhananjay Ramful reiterated Mauritius’ position that its sovereignty over the Chagos archipelago was “non-negotiable”. He also described the 2025 agreement as a vindication of international law and said Mauritius was committed to diplomacy and dialogue over the issue.

Beyond official statements and communiques, the Mauritian government has provided few details about the substance of the current discussions.

International relations consultant Bruno Donat, who has previously worked at the UN, says Mauritius should focus on sustained engagement with diplomatic partners, including the African Union, small island states, the Commonwealth Secretariat and sympathetic voices in the US Congress.

“Being in New York corridors for a photo” is not the priority, Donat says. Sustained engagement, he argues, can build pressure on Washington and prevent the issue from remaining unresolved indefinitely.

The Chagos Refugees Group has pursued a similar approach. In June, two months after the treaty stalled, its members travelled to the UK to lobby representatives of British political parties, with the exception of Reform UK.

The unresolved question of Diego Garcia

But Diego Garcia remains the most contentious part of the agreement.

Lalit, a Mauritian political organisation that has campaigned for decades for the closure of the base, opposes its continued military use. Lindsey Collen of Lalit says the treaty, as it stood in April, would have kept the base open and brought Mauritius into a closer relationship with the US military presence on the island.

“In addition to the moral responsibility, we have the knowledge that we might become a target for self-defence if our land is used this way,” she says.

Collen is also concerned about a new partnership between the Mauritius Police Force and the New Mexico National Guard, as well as what she describes as the “enormous military-looking buildings” of the new US embassy in Mauritius.

Donat argues that the treaty could instead give Mauritius greater leverage over how Diego Garcia is used.

“Mauritius has publicly stated that the strikes launched from Diego Garcia against Iran breached international law,” he says. “That is not the position of a government staying silent to protect a lease payment.”

For Bancoult, those wider strategic questions are secondary to the need to ensure that elderly Chagossians have the chance to return to their homeland during their lifetimes.

“We are opposed to war, ethically, but we are also running out of time.”

The Chagos Refugees Group hopes to soon celebrate the 101st birthday of one of its members.

“God willing, he’ll stay with us for more years,” Bancoult says.