Britain will hand over sovereignty of the Chagos Islands in the Indian Ocean to Mauritius while retaining delegated sovereignty over Diego Garcia, a joint British American military base Britain withheld when granting Mauritius independence in 1968.
In a statement the two governments said they agreed they will sign a treaty recognising that Mauritius is sovereign over the Chagos Archipelago, including Diego Garcia but that Britain will be authorised to exercise with respect to Diego Garcia delegated sovereignty rights to ensure its operation as a military base in the Indian Ocean.
The agreement was concluded with the approval of US President Joe Biden who said it was a good compromise that secures long-term the effective operation of the existing American base on Diego Garcia vital to US and UK regional and global security. American approval, however, is not guaranteed to last if Donald Trump becomes US president on November 5 as he would probably reverse most of Biden’s decisions like he did with most of Barack Obama’s when he succeeded him as president in 2016.
The British foreign office began to think about relinquishing sovereignty over the Chagos Islands after the International Court of Justice (ICJ) ruled in an advisory opinion in 2019 that Britain had retained sovereignty over the islands unlawfully. When she granted independence to Mauritius in 1968 the islands were part of the British colony of Mauritius. On granting independence to Mauritius, however, Britain detached the Chagos Islands from Mauritius and in effect recolonised them as the British Indian Ocean Territories.
Basically the ICJ held that colonial powers could not decolonise lawfully if they recolonised parts of the colonies they were relinquishing. The fact that the Chagos Islands are a distance of a thousand miles from Mauritius was legally irrelevant since it was part of the same colony. Boris Johnson, who as prime minister ignored ICJ decision, has made the argument that the thousand-mile distance justified defying international law. However, his argument is not very clever as the islands are 6,000 miles away from Britain.
International law is frequently declared whenthe UN General Assembly asks the ICJ for an advisory opinion on questions of law. Advisory opinions have great moral and legal force in the rules-based order devised by the West based on respect for the sovereignty of states, human rights and the rule of law.
The Chagos Islanders, who like Mauritians are people mostly of mixed African Indian descent, were not consulted whether they wished to stay British. The biggest island in the archipelago, Diego Garcia was leased to the US in 1966 for use as a military base and the Chagos Islanders were removed from their homeland and forbidden to return.
That was no way to treat people, and it came as no surprise that the ICJ held that a colonial power could not lawfully detach and retain part of a colony without consulting the people affected and that Britain’s continued administration of the Chagos Archipelago including Diego Garcia was wrongful. Britain also detached and retained sovereignty of the British bases (SBA) in Cyprus and it is interesting to speculate how the ICJ decision on the Chagos Islands impacts the bases in Cyprus – but that’s another story especially as the Cyprob complicates proper analysis.
Negotiations to relinquish sovereignty over the Chagos Islands began under the previous Conservative government in 2022 after Johnson was removed from office. It received a boost when the Labour Party came to power in July 2024 and appointed Jonathan Powell who had previously negotiated the Good Friday agreement in Northern Ireland to lead the negotiations.
The trick was to find a compromise that satisfied the ICJ ruling as well as Mauritius and the US. To satisfy the ICJ ruling and the interests of Mauritius, Britain had to recognise the latter’s sovereignty over the Chagos Islands. To satisfy US and British regional and global security needs, it was necessary for Britain to be authorised to exercise sovereign rights over Diego Garcia.
How then to square the circle? It looks as though some clever international lawyer at the British foreign office came up with the idea of delegated sovereignty. Britain declares that Mauritius has sovereignty over the Chagos Archipelago and Mauritius delegates its sovereignty rights over Diego Garcia to Britain for 99 years – Britain needed sovereignty rights to preclude Mauritius from providing facilities to any other power like the Peoples Republic of China with whom it enjoys close relations.
The idea of delegating the authority to exercise sovereign rights from Mauritius to Britain is novel and it remains to be seen how it is converted into a treaty provision and how it is received internationally by other states.
The Conservatives are dead against the agreement. James Cleverly, who started the negotiations in 2022 when he was foreign minister, called the agreement weak. He is now a candidate for leader of the Conservative Party whose decision to start negotiations was criticised by Tom Tugendhat, another candidate. He argues that Britain is not bound by the ICJ opinion and retain sovereignty of the Chagos Islands even if it means continuing to act unlawfully.
Both pander to the irrationality of the extreme right. The fundamental point is that sovereignty had to be relinquished because it was both immoral and illegal to keep it and that guaranteeing use of Diego Garcia for 99 years was a pragmatic compromise that satisfies Britain’s standing in the global south as well as her security needs in the region.
Alper Ali Riza is a king’s counsel in the UK and a former part time judge
