Now, a win for the Chagossians

4 March 2019 by

The International Court of Justice has given a near-unanimous opinion that the separation in 1965 of the Chagos Archipelago from the then British colony of Mauritius was contrary to the right of self determination, and that accordingly the de-colonisation of Mauritius by the United Kingdom had not been in accordance with international law. The ICJ held that Britain’s continued administration of the islands was an internationally wrongful act, which should cease as soon as possible.

This is the latest in a long series of cases concerning the Chagossian islanders, the last domestic one being Hoareau last month, which summarises decisions so far. Also see [120]-[130] of the ICJ’s opinion for the back-story.


The Chagos Archipelago consists of a number of islands and atolls in the Indian Ocean. The largest island is Diego Garcia, which accounts for more than half of the archipelago’s total land area.

Mauritius is located about 2,200 km south-west of the Chagos Archipelago. Between 1814 and 1965, the islands were administered by the United Kingdom as a dependency of the colony of Mauritius. In 1964, there were discussions between America and Britain regarding the use by the United States of certain British-owned islands in the Indian Ocean, in particular in establishing an American base on Diego Garcia.

It was agreed that the United Kingdom would be responsible for acquiring land, resettling the population and providing compensation at its expense; and that Britain would assess the feasibility of the transfer of the administration of Diego Garcia and the other islands of the Chagos Archipelago from Mauritius.

The United Kingdom also commenced talks with the Premier of the colony of Mauritius regarding the detachment of the Chagos Archipelago from Mauritius, culminating in an agreement in 1965 at Lancaster House. This led in 1965 to the establishment of a new colony – the British Indian Ocean Territory (BIOT) consisting of the Chagos Archipelago, detached from Mauritius, and the Aldabra, Farquhar and Desroches islands, detached from Seychelles. In 1968, the remaining territories of Mauritius became independent. Between 1967 and 1973, the entire population of the Chagos Archipelago was either prevented from returning or forcibly removed by the United Kingdom. The UK has subsequently decided against allowing the Chagossians to resettle their islands.

Many claims have been made by those Chagossians removed from their homes in domestic courts and in the European Court of Human Rights, while Mauritius itself has brought claims in the past against the UK for its declaration of a Marine Protected Area around the islands which excluded locals from fishing in those waters. In 2017, the UN General Assembly decided to ask the International Court of Justice for an advisory opinion on (1) whether the process of decolonisation of Mauritius had been lawfully concluded, given that part of its territory was excised before independence was granted by the colonial power, and (2) the legal consequences of the UK’s continued administration of the Chagos Archipelago, including the inability of the Chagossians to return to their homes.

The judgment

The ICJ reviewed the various UK and ECtHR cases brought by Chagossians seeking the right to return to the islands, and noted that

To date, the Chagossians remain dispersed in several countries, including the United Kingdom, Mauritius and Seychelles. By virtue of United Kingdom law and judicial decisions of that country, they are not allowed to return to the Chagos Archipelago.

The first substantive issue was to what extent was there a customary right in international law to self-determination in 1965-8. The ICJ noted the obligation (under Chapter XI of the UN Charter) for UN Member States administering territories with peoples without full self-government to develop the self-government of those peoples. The ICJ held that it followed that

the legal régime of non-self-governing territories, as set out in Chapter XI of the Charter, was based on the progressive development of their institutions so as to lead the populations concerned to exercise their right to self-determination.

The adoption of UN resolution 1514 (XV) of 14 December 1960, which affirmed that “[a]ll peoples have the right to self-determination” represented “a defining moment in the consolidation of State practice on decolonization “the General Assembly has a long and consistent record in seeking to bring colonialism to an end” rather than being about a resolution of a territorial dispute between two states. General Assembly resolution 1514 (XV) clarifies the content and scope of the right to self-determination. The Court notes that the decolonization process accelerated in 1960, with 18 countries, including 17 in Africa, gaining independence. During the 1960s, the peoples of an additional 28 non-self-governing-territories exercised their right to self-determination and achieved independence.

There was a “clear relationship between resolution 1514 (XV) and the process of decolonization following its adoption.” Accordingly, resolution 1514 (XV) indicated that self determination was a customary norm in international law.

The ICJ went on to hold that both State practice and opinio juris at the relevant time confirm the customary law character of the right to territorial integrity of a non-self-governing territory as a corollary of the right to self-determination. It therefore followed that

any detachment by the administering Power of part of a non-self-governing territory, unless based on the freely expressed and genuine will of the people of the territory concerned, is contrary to the right to self-determination.

The second issue was whether the detachment of the Chagos Archipelago had been done in accordance with international law. The ICJ held that at the time of its detachment from Mauritius in 1965, the Chagos Archipelago was clearly an integral part of that non-self-governing territory. The ICJ considered the background to the agreement of the Mauritius Council of Ministers in 1965 to that detachment and held that it is not possible to talk of an international agreement, when one of the parties to it, Mauritius, which is said to have ceded the territory to the United Kingdom, was under the authority of the latter. So heightened scrutiny should be given to the issue of consent in a situation where a part of a non-self-governing territory is separated to create a new colony. The Court considered that this detachment was not based on the free and genuine expression of the will of the people concerned.

Hence, the United Kingdom was obliged under international law as at 1965 to respect the territorial integrity of its colonies, and accordingly,

as a result of the Chagos Archipelago’s unlawful detachment and its incorporation into a new colony, known as the BIOT, the process of decolonization of Mauritius was not lawfully completed when Mauritius acceded to independence in 1968.

With respect to the third substantive issue, the ICJ in short order held that

The Court having found that the decolonization of Mauritius was not conducted in a manner consistent with the right of peoples to self-determination, it follows that the United Kingdom’s continued administration of the Chagos Archipelago constitutes a wrongful act entailing the international responsibility of that State… Accordingly, the United Kingdom is under an obligation to bring an end to its administration of the Chagos Archipelago as rapidly as possible, thereby enabling Mauritius to complete the decolonization of its territory in a manner consistent with the right of peoples to self-determination.

The ICJ essentially side-stepped the issue as to whether it would be adjudicating in a bilateral dispute between Mauritius and the UK over who had sovereignty over the Chagos Archipelago in which one of those states (the UK) did not consent to such adjudication. The questions posed by Mauritius and the General Assembly had refrained from including any reference to sovereignty and the ICJ refused to reformulate or narrow down the question so as to become a bilateral sovereignty dispute. The ICJ acknowledged that “there would be a ‘compelling reason for it to decline to give an advisory opinion when such a reply “would have the effect of circumventing the principle that a State is not obliged to allow its disputes to be submitted to judicial settlement without its consent.’”

It did so by considering that the question from the General Assembly concerned decolonization in which “the General Assembly has a long and consistent record in seeking to bring colonialism to an end” rather than being about a resolution of a territorial dispute between two states. However, the inevitable consequence of its finding that decolonization process concerned was illegal is that either the UK has no sovereignty over the islands, or it does have sovereignty but is obliged to hand over sovereignty to Mauritius.

The ICJ asserted that self determination was a customary rule of international law by 1968. However, it did not do so by reference to contemporaneous state practice or legal opinion. The sole basis for such an assertion was in effect a series of General Assembly resolutions. The ICJ also did not explicitly state how Mauritius could have consented to the detachment of the Chagos Archipelago, although implicitly held that it could only have done so by way of a referendum.

The key significance of the judgment to the UK, and even more perhaps to the US, is the court’s finding that the continued presence of the UK in the Chagos Archipelago is a wrongful act. The UK Government has not yet confirmed whether it will adopt the ICJ’s advisory opinion and hand the Chagos Archipelago to Mauritius.

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