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International: International Tribunal for the Law of the Sea Confirms Sovereignty of Mauritius over Chagos Archipelago

(Feb. 23, 2021) On January 28, 2021, in its Judgment on Preliminary Objections in the Dispute Concerning Delimitation of the Maritime Boundary between Mauritius and the Maldives in the Indian Ocean, the International Tribunal for the Law of the Sea (ITLOS) rejected the Maldives’ challenges to the Tribunal’s jurisdiction. The judgment was rendered by the Special Chamber instituted by the Special Agreement and Notification concluded between Mauritius and the Maldives in 2019 in accordance with article 15, paragraph 2 of the Statute of the International Tribunal for the Law of the Sea. Among its various preliminary objections, the Maldives had challenged the jurisdiction of the Special Chamber, arguing (1) that the United Kingdom (U.K.) was an indispensable third party to the dispute and (2) that sovereignty over the Chagos Archipelago is disputed.

Given the Maldives’ preliminary objections, the Special Chamber thus inquired into the legal status of the Chagos Archipelago, over which the U.K. claims sovereignty as the British Indian Ocean Territory (BIOT). With reference to previous international legal determinations on the issue (the Chagos arbitral award, the Chagos advisory opinion, and United Nations General Assembly Resolution 73/295), the Special Chamber found that (1) any interests the U.K. may have with respect to the Chagos Archipelago are not “sufficient legal interests” and (2) Mauritius is the “coastal state in respect of the Chagos Archipelago for the purpose of the delimitation of a maritime boundary even before the process of the decolonization of Mauritius is completed.”

Brief Background to the Dispute

Before Mauritius gained independence from the U.K. in 1968, the U.K. separated the Chagos Archipelago from Mauritius in 1965. In the following years, the U.K. forcibly resettled thousands of inhabitants from the islands. The U.K. also leased the largest island of the archipelago, Diego Garcia, to the United States, where it established a military base as a strategic asset in the Indian Ocean. Mauritius has continuously contested U.K. sovereignty over the Chagos Archipelago, arguing that it was coerced into giving up the islands and that the separation of the archipelago from the former British colony was in violation of several U.N. resolutions on decolonization, including Resolution 1514 (1960), which banned the breakup of colonies before independence.

In 2017, the U.N. General Assembly asked the International Court of Justice (ICJ) to render an advisory opinion on two questions relating to the legal consequences of the separation of the Chagos Archipelago from Mauritius in 1965. In 2019, the ICJ found that the decolonization of Mauritius had not been lawfully completed and that it must be completed as rapidly as possible. Following the advisory opinion, the General Assembly demanded that the U.K. withdraw its colonial administration from the archipelago within six months, enabling Mauritius to complete the decolonization of its territory.

What’s Next for the Chagos Archipelago?

Since October 2020, the U.N. official world map indicates the Chagos Archipelago as Mauritian territory. Despite these international legal determinations and institutional adjustments, the U.K. has continued to express that it has “no doubt” about its sovereignty over the Chagos Archipelago, and that it will stand by its “long standing commitment, first made in 1965, to cede sovereignty of the territory to Mauritius when it is no longer required for defence purposes.”

Meanwhile, the Dispute Concerning Delimitation of the Maritime Boundary between Mauritius and the Maldives in the Indian Ocean will continue with the Special Chamber at ITLOS. However, some have argued that the next step in this fight over the Chagos Archipelago will occur in the Indian Ocean Tuna Commission (IOTC), the intergovernmental authority established by the U.N. Food and Agriculture Organization in 1996 to regulate fishing in the region. The U.K. is currently an IOTC member by virtue of its claim to sovereignty over the Chagos Archipelago and BIOT as a coastal state in the Indian Ocean, but Mauritius is lobbying to expel the U.K. from the IOTC.