Why is the UK negotiating BIOT sovereignty with Mauritius?

One surprising outcome of Liz Truss’s brief and ill-fated period as UK Prime Minister was her decision to begin negotiations with Mauritius over the sovereignty of the Chagos Islands.


Craig Brewin

4/2/20247 min read

One surprising outcome of Liz Truss’s brief and ill-fated period as UK Prime Minister was her decision to begin negotiations with Mauritius over the sovereignty of the Chagos Islands. Despite international pressure and various legal judgements, the UK has consistently refused to do this, and her decision surprised many people. These included James Cleverly, who inherited responsibility for the talks when he became Foreign Secretary and had to make the announcement. This was in November 2022, and we have heard little since then other than that the military base would remain unaffected.

So, what happened, and how did we get here? The Chagos Islands have been British since the Treaty of Paris ceded them to the UK after the fall of Napoleon, and the large military base on Diego Garcia was built under a post-war bilateral agreement with the USA. This base is strategically important, and the location was chosen for being within bombing range of Russia and China. It is also now used as a base for operations in the Middle East, and is close to busy shipping lanes. It is seen as an important location for monitoring and tackling drug trafficking, piracy and crime in the Indian Ocean, and has been used as a base for supporting humanitarian responses, such as after the 2004 tsunami. So why was Liz Truss willing to hand them over to Mauritius?

This article explains the background of the negotiations rather than making a case for an outcome. The UK has always said that the future of the islands will be the subject of bilateral talks with Mauritius, but that this will be when the military presence is no longer required. Realistically, this was unlikely to happen in the lifetime of anyone reading this. The USA, which demanded the islands be depopulated, has been strategically quiet but is undoubtedly discreetly involved behind the scenes. The Chagossian people who wanted British citizenship now have it, but still have no voice in the debate over the future of the islands. The archipelago was depopulated for a reason: to ensure that the islanders had no right to self-determination under the UN’s decolonisation process.

To understand why Liz Truss felt it was in the UK’s interests to start negotiating we need to understand recent case law. These cases have not been about the rights of the Chagossians but geo-political power. No one has challenged the view that the islands have no population, and the previous Labour leadership supported the campaign of Mauritius based Chagossians who were backing the Mauritius claim. The SNP have called for the UK to end its illegal occupation. However, the Chagossians forcibly removed from the islands still have no right to self-determination under international law.

The legal issues stem from what the British called the “policy of detachment”. Post-war decolonisation was meant to happen using historic colonial borders. Simply put, this is why the Falklands, which was a British colony, and Argentina, which was Spanish, are not politically connected. This is probably why Argentina, for all its bluster, has never sought the same legal arbitration that Mauritius has over the Chagos Islands – even though Mauritius won. Mauritius and the Chagos Islands were governed by the British as a single colony and, under UN rules, should have been decolonised as a single entity. It is a unique situation, which means the UN has resolved that the decolonisation of Mauritius is incomplete, even though the Chagos Islands are not on the UN list of non-self-governing territories.

The detachment was done by an Order in Council approved in November 1965 and was therefore never discussed in the UK parliament. It was also rushed through to get the detachment done before anyone noticed. The imperative was to avoid “a delay long enough to allow the United Nations or anybody else to start a campaign against the policy”, according to a note in the files of the colonial office. There was a genuine concern that if the British Indian Ocean Territoiry was not created immediately, “the policy could be seriously jeopardised and might even have to be abandoned”.

The policy of detachment was also applied to the Seychelles, with the atols of Desroches, Aldabra and Farquhar, detached and included within BIOT. These were returned to the Seychelles when it achieved independence in 1976 and Desroches is now a luxury holiday destination. It took several years to depopulate the new BIOT. Several means were used, including barring people who had left temporarily from returning, killing all the dogs, and ultimately, putting the last remaining residents in the hold of a cargo ship. Not all had family members on other islands, with some described in a memo written by a British civil servant as Tarzans and Man Fridays of no determinate origin. Several of those born there were in attendance at the last FOTBOT reception on the issue, and are still fighting for compensation for the generational trauma. However, as stated above, the current debate concerns something other than the Chagossians. It is, in fact, about the sea.

The legal decision that sent the UK Government to the negotiating table resulted from a dispute between the Maldives and Mauritius over its territorial waters. In 2015, Mauritius received a judgement from the United Nations Arbitral Tribunal that commitments made by the UK in 1965 on fishing, oil, and mineral rights became binding upon independence. This ruling effectively made the Marine Protection Zone, set up by the UK around the islands in 2010, illegal. The UK accepted this judgement but later pointed out to the International Court of Justice that this agreement also states that the islands would be returned to Mauritius when they are “no longer required for military purposes”. In its evidence to the ICJ, the UK said this agreement meant the future of the islands was a bilateral issue and not within the remit of the Court.

However, in an Advisory Opinion delivered in 2019, the ICJ concluded that “the process of decolonisation of Mauritius was not lawfully completed when that country acceded to independence” and that “the United Kingdom is under an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible”. This was an advisory judgement made at the request of the UN General Assembly, but the legal issues did not end there.

In 1982, the UK signed the UN Convention on the Law of the Sea, which established an International Tribunal (ITLOS) whose decisions are final and binding. In 2021, Mauritius took a case there to determine the sea boundary between the Maldives and Mauritius. Maldives argued that the islands were subject to a territorial dispute and ITLOS, therefore, had no jurisdiction. But the Tribunal would not accept that. It ruled that the territorial controversy between the UK and Mauritius was settled and the islands and the sea around them belonged to Mauritius.

Opponents of the negotiations, such as Henry Smith MP, who also attended FOTBOT’s Chagos reception earlier this year, have argued that the General Assembly vote on the 2019 ICJ ruling was “basically all of our enemies lining up to say Britain’s a horrible colonial power and to give things back. The likes of the Chinese, the Russians, the Iranians—of course, they’re going to vote against Britain.” But the issue is more complex and, in any case, Britain lost the vote in the General Assembly by 116-6. That’s a lot of enemies, and only five friends. These were Maldives and the USA, which was no surprise, but also Israel, Hungary and Australia.

Should both sides be talking? Liz Truss said yes, and it is difficult to argue it is a bilateral dispute and then not talk to the other party. However, there has been opposition within the Conservative Party, with Boris Johnson being the highest profile and Daniel Kawczynski being the most vociferous. Kawczynski has claimed that the Mauritian free trade agreement with China puts Mauritius within China’s sphere of influence and that the negotiations should, therefore, stop immediately.

At a meeting in the House of Commons last year, at which I was present, Kawczynski told Human Rights Watch, who were presenting a report on the human rights of Chagossians, that stopping the negotiations with Mauritius was the only thing that mattered at this point. This followed previous comments he made on the matter that pre-date Truss’s decision to negotiate. Attacking those who argued that the UK should not be challenging the rules-based international order, he said; “If the BIOT is ceded to Mauritius, I have little doubt that it will not be long before the naval facilities at Diego Garcia join Xi Jinping’s ‘string of pearls’ – and become an anchor for a very different world order”. That may be far-fetched given that up to 5,000 US military personnel are on Deigo Garcia, and the final agreement will need approval from the USA. But Henry Smith has said that whatever the final outcome of the negotiations, China will inevitably see it as an opportunity.

It is worth pointing out that Cleverly’s announcement did not explicitly change the UK position. However, he did confirm that sovereignty would be an issue in the talks. He said: “It is our intention to secure an agreement based on international law to resolve all outstanding issues, including those relating to the former inhabitants of the Chagos Archipelago. This will allow the UK and Mauritius, as close Commonwealth partners, to work even more closely together to tackle the regional and global security challenges that face us all. We will seek to strengthen significantly our cooperation on Indian Ocean security, maritime security and marine protection, the conservation of the environment, climate change, respect for human rights, and to tackle illegal migration, illegal fishing, drugs and arms trafficking, as well as bilateral cooperation on a range of other issues.” The expected outcome is a plan to transfer sovereignty to Mauritius while retaining the base.

Still missing from all this is the voice of the Chagossian people and the fact that everyone seems to agree that they have no right to self-determination. The ICJ judgment said that the right to self-determination was exercised in the policy of detachment, but this was the right to self-determination by all people living within the former colonial borders, not just Chagossians.

Personally, I am slightly proud of my minor role in supporting the successful Chagossian campaign for British citizenship, particularly as the issue was not even raised in the initial consultation on the Borders and Nationality Bill. In my view, the Chagossian voice should now be heard in discussions over the future sovereignty of the islands. That is unlikely to happen, and the outcome of the negotiations is well overdue, but there has been a suggestion that we will see the agreement before the US presidential election. Expect some fireworks.