Chagos Archipelago: US President signs off UK’s handover of Chagos Islands to Mauritius

7 April 2025.

US President Donald Trump has signed off on the UK’s handover of the Chagos Islands to Mauritius, as Downing Street has indicated, paving the way for the UK to cede sovereignty over its last African colony after a six-month standoff [1]. A spokesperson for British Prime Minister Sir Keir Starmer said on 1 April that the UK welcomed Trump’s recognition of the strength of the Chagos deal and that London was pleased with how the deal was progressing [2]. The prime minister’s spokesperson also stated that the deal was being finalised after receiving the green light from Trump and added: “[m]y understanding is it’s now between us and the Mauritian government to finalise the deal, following the discussions with the US” [1].

Representatives from Mauritius and the UK held further discussions in London last week on the future of the Chagos Archipelago. In a joint statement, the Mauritian government reiterated Downing Street’s comments, stating that both countries were “currently working to finalize this agreement” [3]. The statement also included provisions that “[b]oth countries reiterated their commitment to concluding a treaty confirming that Mauritius is sovereign over the Chagos Archipelago and that would ensure the long-term, secure, and effective operation of the base on Diego Garcia” [4]. Under the proposed agreement, Mauritius would gain sovereignty over the islands from the UK, but the US and UK would continue operating a military base on one of the islands for an initial period of 99 years, at a cost to the British taxpayer [3].

Implications for State Succession

The implications for state succession over Chagos are mainly discussed in the State Succession Watchlist 2025. It could be added that the transfer of the Chagos Archipelago from the UK to Mauritius represents a significant instance of resolving historical territorial disputes through diplomatic means. It underscores the role of international legal bodies, such as the ICJ, in influencing state behavior and resolving colonial-era disputes.

The Chagos Archipelago case carries important implications for state succession, particularly in relation to territorial title, treaty obligations, and international responsibility. Further developments, particularly in UK-Mauritius negotiations, US lease arrangements, and the final treaty text, will be crucial in shaping the final form of state succession, whether framed as restoration, transfer, or continuation of sovereignty.

Sources:

State Succession Index

7 April 2025.