Keir Starmer Chagos Deal Dealt ‘Crushing Blow’ as Judge Rules Chagossians Have Right to Live on Disputed Islands

A high-stakes diplomatic gamble by Sir Keir Starmer has hit a major legal roadblock. In a stunning reversal of decades of British policy, Justice James Lewis KC, Chief Justice of the British Indian Ocean Territory (BIOT) Court, has ruled that native Chagossians have a legal right of abode on the islands.

This judgment directly challenges the Labour government’s controversial plan to hand sovereignty of the Chagos Archipelago to Mauritius.

The ruling effectively prevents the immediate removal of a group of islanders who recently returned to the territory, signaling a potential collapse of the deal that Starmer argued was “vital” for UK-US national security.

Why has a Judge blocked the Chagos Islands handover?

The ruling stems from a dramatic expedition in early 2026, where four Chagossian native-born citizens, including Misley Mandarin, First Minister of the Chagossian Government-in-Exile, landed on Île du Coin in the Peros Banhos atoll.

When the BIOT Commissioner issued removal orders to deport them, the group took the matter to the BIOT Supreme Court.

HUGE NEW BLOW for Starmer’s Chagos deal!

British Indian Ocean Territory Supreme Court JUST ruled Chagossians hold a lawful Right of Abode on Chagos!

Starmer’s deal was signed on the opposite basis – so it is in the SHREDDER

Another gd week on CHAGOS!pic.twitter.com/x1DwcaEpZc

— Ross Kempsell (@RossKempsell) March 31, 2026

Justice James Lewis granted a landmark injunction, reasoning that:

• National Security Arguments are Void: For 60 years, the UK has argued that the islands must remain unpopulated for the security of the Diego Garcia airbase. However, the government’s own deal with Mauritius permits resettlement, meaning the UK can no longer claim that a civilian presence is a security risk.
• Invalidation of 2004 Laws: The ruling effectively overturns the 2004 Immigration Order introduced by Tony Blair’s government, which was specifically designed to prevent the displaced population from returning.
• The Mauritius Paradox: Justice Lewis noted that if the UK admits the islands can be lived on by others under Mauritian rule, it cannot legally deny that same right to British Chagossian citizens now.

Where is the ‘Battle for Chagos’ taking place?

The legal and physical standoff is spanning three key locations across the globe:

• Peros Banhos Atoll (Île du Coin): Located roughly 120 miles from the Diego Garcia base, this is where the four islanders are currently residing under court protection.
• Diego Garcia: The “footprint of freedom” military base. While not directly affected by the physical occupation, the legal status of the surrounding islands impacts the long-term lease agreement.
• The BIOT Court of Appeal (London/Remote): The UK government has already lodged an appeal against Justice Lewis’s ruling, setting the stage for a constitutional showdown in the coming weeks.

Is the £51 billion cost estimate accurate?

One of the most explosive elements of the ruling was Justice Lewis’s reference to the financial burden on the UK taxpayer.

While the Starmer government has cited a “net present value” of £3.4 billion, the judge highlighted figures suggesting the nominal total over the 99-year lease could soar toward £51 billion.

Breaking Down the Estimated Costs

Justice Lewis argued that if the government is prepared to commit such vast sums to a deal that includes resettlement, the previous argument that returning the islanders is “too expensive” no longer holds legal water.

How will this impact the UK public and security?

The ruling creates three distinct waves of impact within the United Kingdom:

1. The ‘Right of Return’ for UK Chagossians

Thousands of Chagossians living in Crawley and Manchester may now have a legal basis to claim resettlement. If the “right of abode” is upheld on appeal, it could trigger a mass migration from the UK back to the Indian Ocean.

2. Strained Relations with the Trump Administration

The timing could not be worse for No. 10. Donald Trump has publicly labeled the deal “an act of great stupidity.”

US officials are concerned that Mauritian sovereignty could allow China to gain a foothold near Diego Garcia. This court ruling gives the US further leverage to demand that Starmer “pauses or cancels” the transfer.

3. Political Instability in Westminster

Nigel Farage and Reform UK, who reportedly helped fund the expedition to the islands, are using the ruling to paint Starmer as a “weak” leader, surrendering British territory.

The Conservative Party has also called for an immediate halt to the implementation of the legislation currently in the House of Lords.

How Does the ‘Trump Factor’ Complicate the Deal?

The legal ruling arrives at a moment of extreme diplomatic tension. The incoming US administration has expressed deep hostility toward the transfer, fearing that Mauritian control could provide a “back door” for Chinese influence in the Indian Ocean.

These geopolitical tensions have intensified as the Trump administration criticizes the Chagos deal while simultaneously pushing for expanded territorial interests elsewhere.

The convergence of a domestic legal defeat and a major rift with the White House leaves the Prime Minister with very little room for maneuver.

What is the Official Government Position?

The Foreign, Commonwealth & Development Office (FCDO) has remained defiant. A spokesperson stated: “The UK remains committed to the treaty with Mauritius, which is the only way to provide long-term legal certainty for the base at Diego Garcia.

We are appealing the BIOT Court’s decision to ensure the rule of law is maintained and that illegal occupations do not dictate foreign policy.”

However, legal experts suggest that if the BIOT Court of Appeal upholds Justice Lewis’s ruling, the treaty with Mauritius may be “unperformable” under international law, as the UK would be ceding territory that its own courts have ruled belongs to a specific group of citizens with rights of abode.

The Expert View: Is this the end of the deal?

James Tumbridge, the barrister representing the Chagossians, told: “This isn’t just a win for my clients; it’s a win for the principle of self-determination.

You cannot trade people like tokens in a game of risk. The government’s position has collapsed under its own contradictions.

They said it wasn’t safe, then they said it was safe for Mauritius. They said it wasn’t affordable, then they offered billions. The judge simply held up a mirror to those inconsistencies.”

Frequently Asked Questions 

Can Keir Starmer ignore the judge’s ruling?

No. The BIOT Supreme Court has jurisdiction over the territory. The government must either win on appeal or pass new primary legislation in Westminster that explicitly overrides the court, a move that would be legally and politically explosive.

Why is Mauritius involved if the islanders want to be British?

Mauritius claims the islands were illegally detached from it in 1965. The International Court of Justice (ICJ) supported this claim in 2019. However, many Chagossians prefer to remain under British sovereignty rather than Mauritian rule.

Does this affect the Diego Garcia airbase?

Directly, no. The base is on a separate island. However, if the “outer islands” become a legal battlefield, it complicates the security perimeter and the 99-year lease Starmer is trying to secure.

What happens to the islanders currently on Île du Coin?

They are currently protected by an interim injunction. They cannot be forcibly removed until the full judicial review is concluded, which could take months.