Landmark ruling for Chagossian rights — and a new legal context for the future of BIOT

Key points:

• Chagossians now have a lawful Right of Abode The Court struck down Section 9 of the 2004 Constitution, overturning the ban that prevented Chagossians from living in their homeland for more than 50 years.

• The Court confirms there was a settled population The judgment rejects the long‑standing fiction that the islands were uninhabited, noting that “by the 1960s it is clear there was a settled population.”

• Historical policy of forced removal is acknowledged The Court cites internal government documents showing deliberate efforts to remove the population and conceal their existence from the UN.

• New legal context makes the ban indefensible The ruling draws on the 2015 feasibility study, the ICJ Advisory Opinion, and the UN General Assembly resolution urging resettlement.

• The ruling directly affects the UK–Mauritius treaty The treaty was drafted on the assumption that BIOT has no resident population. Today’s judgment changes that legal foundation before ratification.

• Chagossians become rights‑holders, not stakeholders Any future governance arrangements must now reflect their legally recognised right to live in the islands.

• The judgment opens a pathway to the UK Supreme Court The case can now be escalated, strengthening the push for a lawful and sustainable resettlement plan.

• A major step for self‑determination The ruling restores a right that should never have been removed and marks a turning point in the long struggle for justice.

• The judgment highlights that the UK–Mauritius treaty could cost the UK up to £50bn over its 99‑year lifespan The Court notes that when the treaty’s obligations — including the 99‑year Diego Garcia lease, environmental commitments, infrastructure responsibilities, and ongoing administrative costs — are modelled with a 3% annual inflation assumption, the total long‑term cost to the UK could reach £50bn. This figure is not about resettlement; it reflects the projected financial burden of the treaty itself. The ruling therefore introduces a major fiscal consideration for Parliament as it debates ratification.

Friends of the British Overseas Territories welcomes today’s landmark judgment from the Supreme Court of the British Indian Ocean Territory, which has ruled that Chagossians hold a lawful Right of Abode in the Chagos Archipelago. This decision overturns more than fifty years of policy and marks one of the most significant legal developments in the history of the Territory.

For the first time, a BIOT court has struck down the constitutional ban that prevented Chagossians from living in their homeland. Section 9 of the 2004 Constitution — which stated that “no person has the right of abode in the Territory” — has been quashed. The Court found that the provision was unlawful, restoring a right that had been denied for generations.

This ruling is rooted in a clear recognition of historical truth. The Court confirms that the Chagos Islands did have a settled population, rejecting the long‑standing fiction that the islands were uninhabited. As the judgment notes, “by the 1960s it is clear there was a settled population… this fact was expressly conceded by the Commissioner.” The Court also recounts the deliberate policy of forced removal and the efforts to conceal the existence of the population from international scrutiny.

The judgment reflects a shifting legal landscape. It draws on new evidence, including the 2015 feasibility study showing that resettlement is viable, and acknowledges the persuasive weight of the International Court of Justice advisory opinion and the UN General Assembly resolution urging the UK to facilitate resettlement. Together, these developments create a compelling basis for revisiting the constitutional framework governing the Territory.

Importantly, today’s ruling has direct implications for the UK–Mauritius treaty on the future of BIOT, which has been signed but not yet ratified by Parliament. The treaty was drafted on the assumption that the Territory has no resident population and that Chagossians have no legal right to live there. The Court’s decision changes that foundation. Chagossians are now recognised as rights‑holders, and any future arrangements for the archipelago must reflect those rights.

The ruling also opens a new legal pathway. The judgment can now be taken to the UK Supreme Court, strengthening the case for a clear, lawful, and sustainable plan for resettlement.

Friends of the British Overseas Territories celebrates this historic affirmation of Chagossian rights. We also recognise that the ruling creates a new legal context for the treaty currently before Parliament. It is essential that the next steps — whether legislative, diplomatic, or administrative — fully respect the rights recognised by the Court and support a stable, inclusive, and just future for the Territory.

We will continue to monitor developments closely and provide updates as the situation evolves.