Mauritius and the Maldives, situated in the north central Indian Ocean, share a maritime boundary positioned between the southernmost tip of the Maldives Archipelago and the northernmost features of the Chagos Archipelago. The boundary, which consists of 38 turning points, begins in the west, and extends for 308 nautical miles on an easterly course until reaching the Parties’ respective 200 nautical mile limits. The boundary does not divide the extended continental shelf claims of the Parties, which may require a delimited boundary in the future.

The boundary was determined by a Special Chamber of the International Tribunal for the Law of the Sea (ITLOS). The two States sought the help of ITLOS in 2022 to resolve the question of whether Blenheim Reef, a feature located at the northeastern tip of the Chagos Archipelago, should be taken into consideration for the plotting of an equidistance boundary. At stake were roughly 92,563 square kilometers of overlapping exclusive economic zone entitlements.

A judgment was delivered by the Tribunal on 28 April 2023 that defined the maritime boundary in detail. It determined that Blenheim Reef should be given partial effect, splitting the area of overlapping entitlements almost perfectly in half. While the issue over Blenheim Reef was resolved, the conflict over the two States’ claims in the outer continental shelf continues. In its Judgement, ITLOS found that it could not, with the information before it, define a boundary dividing the Parties’ extended continental shelf claims.

The situation was further complicated by the sovereignty dispute over the Chagos Archipelago between Mauritius and the United Kingdom. In 2019, the International Court of Justice (ICJ) issued an advisory opinion to the United Nations General Assembly on the subject, noting that the Chagos Archipelago was unlawfully detached from the colony of Mauritius in 1965 by the United Kingdom, and that the decolonization of Mauritius, who gained independence in 1968, had not been lawfully completed. The United Kingdom was instructed by the ICJ to end its illegal occupation of what it calls the British Indian Ocean Territory (BIOT). Despite Mauritius’ de jure sovereignty over the Chagos Archipelago, the United Kingdom maintains de facto control of the region.