Sovereignty Disputes

Disputes over the British Indian Ocean Territory: a survey

An in-depth House of Commons Library briefing by Dr John Lunn summarises past and present disputes over the BIOT:

Between 1968 and 1973 the British Government cleared the entire Chagos Archipelago of its inhabitants, opening the way for a US military base on the biggest island, Diego Garcia. The Archipelago was made a British overseas territory, the British Indian Ocean Territory (BIOT). Two main disputes have arisen from these events. One has been between the Chagos Islanders and the British Government over the legality of the former’s removal and whether they have a right to return. The other has been between the UK and Mauritius about sovereignty over the BIOT. The UK has said that it will cede sovereignty to Mauritius once the BIOT is no longer required for defence purposes.

Can progress be made towards resolving these disputes? Both have at various points in the past appeared to be all but intractable and several domestic and international legal challenges remain in play. But potential ways forward over the next two years are certainly not beyond the bounds of imagination. The British Government is currently reviewing its policy on resettlement, with supporters of the Chagos Islanders arguing that the outer islands of the Archipelago could be feasible sites for limited resettlement. And while the arrangement with the US over its military use of Diego Garcia looks set to be extended for a further 20 years from 2016, some are asking whether, if the outer islands of the BIOT are not required for defence purposes, they could be ceded to Mauritius as an interim step.

This paper surveys the origins and complex subsequent evolution since 1965 of these separate but inter-related disputes over the Chagos Archipelago. It concludes by exploring the prospects for making progress towards resolving these disputes over the next couple of years.

The original paper: Disputes over the British Indian Ocean Territory: a survey - Commons Library Research Paper

John Lunn has provided periodic updates to his paper. The latest is dated 28 May 2019: Disputes over the British Indian Ocean Territory: May 2019 update

UK Claim that an International Arbitral Tribunal has upheld its claim to sovereignty

The United Kingdom has recently claimed that its agreement with the Mauritian Council of Ministers in 1965 to the detachment of the Chagos Archipelago from Mauritius has been found to be legally binding in international law by virtue of the Award of an UNCLOS Arbitral Tribunal in 2015. A paper (November 2019) by Richard Dunne demonstrates why this claim is unfounded. The UK Government has been asked to explain the legal basis for its claim but to date has been unable to provide any reasoned argument. Its earlier arguments to support the claim before the International Court of Justice in 2018 were fundamentally flawed and were rejected by that court. The full paper is available : Dunne 2019 Legal Status of Lancaster House Agreement 1965