Mauritius v. Maldives: One Judgement, Two Victors


ITLOS implemented the three-stage approach to delimit the overlapping maritime area of Mauritius and the Maldives. ITLOS carried out the following steps: (1) Construct a provisional equidistance line between the coasts of Mauritius and the Maldives; (2) Adjust the equidistance line to suit the relevant circumstances of the maritime area that needs to be delimited, particularly the environmental and geographical factors of the Blenheim Reef (in the Chagos Archipelago); (3) Check whether or not the adjusted equidistance line was equitable and fair (ITLOS did not find any significant difference between the ratio of the countries’ coastal lengths and the ratio of the relevant maritime areas allocated to each country, therefore ITLOS decided to maintain the equidistance line drawn in step two).

The three-stage approach was first formulated by the ICJ in the dispute over the Black Sea (Ukraine v. Romania, 2009). It was then used in Bangladesh v. Myanmar (2012), and Kenya v. Somalia (2021).

Accordingly, the maritime area allocated to Mauritius is 45.331 square kilometers, while that of the Maldives is 47.332 square kilometers. The ratio is 1:0.960 in favor of the Maldives. This result is not inconsistent with the ratio of the coastlines of the two countries, which is 1:1.03 in favor of Mauritius (the coastline of Mauritius is 40.3 kilometers and that of the Maldives is 39 kilometers).


In 2019, Mauritius requested ITLOS to delimit the overlapping maritime area with the Maldives in the Indian Ocean. Initially, the Maldives objected to ITLOS’s jurisdiction because the sovereignty over the Chagos Archipelago was being disputed. The Chagos Archipelago was once part of the Mauritius colony of the UK, and since Mauritius’s independence in 1968, it has been the focus of a sovereignty dispute between Mauritius and the UK. According to the Maldives, the UK was an indispensable third party in this case. However, the UK refused to participate. Due to this absence, the Maldives claimed that the Court did not have the jurisdiction to consider Mauritius’s request.

ITLOS rejected the argument of the Maldives in its preliminary Judgment of 28 January 2021. ITLOS affirmed that the Chagos Archipelago belonged to Mauritius, not the UK. ITLOS based its reasoning on the 2019 Advisory Opinion of the International Court of Justice (ICJ) on the legal consequences of the separation of the Chagos Archipelago from Mauritius in 1965. According to the Advisory Opinion, the UK's separation of Chagos from the colony of Mauritius was a violation of international law. Consequently, ITLOS declared that the UK was not an indispensable party to the dispute and that its absence would not affect ITLOS's jurisdiction over the dispute between Mauritius and the Maldives.


ITLOS's recognition of the "legal effect" of ICJ's 2019 Advisory Opinion has contributed to the development of international law. According to ITLOS, while ICJ's Advisory Opinions are not binding, they still have a legal effect because of their authoritative nature. The process of drafting ICJ's Advisory Opinions is extremely complicated and rigorous, no lesser than that of the judgment drafting procedure. Moreover, ICJ is known as the "World Court", which is the judicial body of the United Nations. Therefore, legally, ICJ's Advisory Opinions naturally carry weight. This conclusion of ITLOS will elevate the importance of ICJ Advisory Opinions when disputes potentially arise between states in the future.

In addition, the preliminary Judgment of 28 January 2021 and the recent final Judgment of 28 April 2023 are a major victory for Mauritius in the sovereignty dispute over the Chagos Archipelago. The two rulings further strengthen Mauritius's sovereignty over the Chagos Archipelago legally and increase support for Mauritius at the international level. Although the UK rejected the ICJ's 2019 Advisory Opinion as non-binding and has not participated in the dispute, the two rulings will put pressure on the UK to return the Chagos Archipelago to Mauritius.


Mauritius and the Maldives both celebrate ITLOS’s Judgment of 28 April 2023. In the Mauritius government's press release, Mauritius announced that the ruling has once again established Mauritius's sovereignty over the Chagos Archipelago. Maldivian officials attempt to paint this Judgment as a legal victory: President Ibrahim Mohamed Solih called the ruling a great win for the Maldives, and a key milestone that established the Maldives' southern maritime boundary. However, the Maldives' opposition argued that the ruling had caused "irreparable damage". The Maldives’ opposition party has a history of using the Chagos Archipelago issue and the maritime delimitation issue to criticize the government, so this reaction is not unexpected.

Ngân Hà

An original version of the article was published here