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The Chagossian Question: The ICJ Advisory Opinion and Its Implications

- Khushi and Smrithi Suresh

Background of the Dispute

The Chagos Archipelago is a group of islands located in the Indian Ocean, south of the Maldives and about 500 kilometres east of the Seychelles. The archipelago consists of more than 50 small islands, with the largest being Diego Garcia, also the only inhabited island.

The Chagos islands were originally settled by the French in the 18th century and later became a British colony in the 19th century. In the 1960s, the Lancaster House Agreement was signed between the representatives of the colony of Mauritius and the United Kingdom Government regarding the detachment of the archipelago from Mauritius, which resulted in the creation of the British Indian Ocean Territory [“BIOT”], which is now a British Overseas Territory. Additionally, there was an agreement between the United States of America and the United Kingdom for the installation of a military base by the United States on the islands.

The construction of the military base required the forced removal of the Chagossian people, who were the original inhabitants of the islands. They are primarily of African, Malagasy, and Indian descent and were brought to the islands as indentured labourers in the 18th and 19th centuries. The Chagossians were forcibly evicted from the islands between 1967 and 1973 and were resettled in Mauritius and the Seychelles. In fact, in April 1971, the BIOT Commissioner enacted the Immigration Ordinance, which essentially made it unlawful for any person to enter or remain in the Chagos Archipelago without a permit.

The sovereignty of the Chagos Archipelago is still a subject of dispute, with both Mauritius and the United Kingdom claiming ownership, even when Mauritius gained independence as far as back in 1968. The United Kingdom, in 2010, announced the creation of a marine protected area in and around Chagos islands, which was contested by Mauritius before an Arbitral Tribunal pursuant to the UNCLOS. In 2015, the Tribunal held that Britain had breached its obligations under the UNCLOS and that it must return the archipelago to Mauritius as it is no longer needed for defence purposes.

The ICJ’s Advisory Opinion

The United Nations General Assembly [“General Assembly”] adopted Resolution 71/292 in 2017 wherein it requested for the advisory opinion of the International Court of Justice [“the Court”] on this matter. This was officially communicated to the Court by the Secretary-General of the United Nations.

Two major questions were put forth in the resolution:

  1. Was the process of decolonisation of Mauritius lawfully completed when Mauritius was granted independence in 1968, following the separation of the Chagos Archipelago from Mauritius and having regard to international law, including obligations reflected in several General Assembly resolutions?

  2. What are the consequences under international law arising from the continued administration by the United Kingdom of Great Britain and Northern Ireland of the Chagos Archipelago, including with respect to the inability of Mauritius to implement a programme for the resettlement on the Chagos Archipelago of its nationals, in particular those of Chagossian origin?

Preliminary jurisdiction

The Court first analysed whether it had jurisdiction over the matter. Art. 65 ¶ 1 of the ICJ Statute provides for an advisory jurisdiction by the Court on any legal question at the request of any body authorised by the UN Charter. Here, the General Assembly is competent to request the Court by virtue of Art. 96 ¶ 1of the Charter.

The Court, further, decided that the request by the Assembly is, in fact, regarding a legal question and “lack of clarity” as alleged does not deprive the Court of its jurisdiction to render the advisory opinion.

The Court’s Opinion

Question 1:

The Court stated that the UN Charter includes clauses that would eventually allow non-self-governing areas to exercise self-government, since support for the principle of equal rights and peoples’ right to self-determination is one of the purposes of the UN.

Moreover, custom is constituted through general practice accepted as law.” Various resolutions in the spirit of decolonisation have been passed by the General Assembly, especially, resolution 1514 (XV) which clarifies the content and scope of right to self-determination. Despite being formally a recommendation, this resolution has a declarative nature addressing the right to self-determination as an accepted standard. In the Friendly Relations Declaration of 1970, the nature and extent of the right to self-determination of peoples, including respect for “the national unity and territorial integrity of a State or country “were reaffirmed as part of the customary principles of international law.

The Court opined that the law on self-determination was the applicable international law during the period under consideration, i.e., the period between the separation of the Chagos Archipelago from its territory in 1965 and Mauritius’ independence in 1968.

It held that when the detachment of Chagos Archipelago from Mauritius was agreed to by the Council of Ministers in the Lancaster House Agreement, Mauritius was in fact a colony of the United Kingdom and its representatives did not have any real legislative or executive powers. Thus, the decision on this agreement was not based on the free and genuine expression of the will of the people concerned.

Therefore, the Court arrived at the conclusion that due to the unlawful nature of the detachment of the archipelago and the subsequent incorporation into BIOT, the process of decolonisation of Mauritius was not lawfully completed at the time of Mauritius’s independence in 1968.

Question 2:

The Court, having stated the decolonisation to be incomplete, held that the continued administration of the archipelago by the United Kingdom is a wrongful and unlawful act of a continuing character. The United Kingdom was held to be obligated to end its administration of Chagos as rapidly as possible.

The subsequent modalities were left to the General Assembly for ensuring the completion of the decolonisation. As respect for the right to self-determination is an obligation erga omnes, naturally all States have a legal interest in protecting it.

Regarding the resettlement of the Mauritian nationals, especially those of Chagossian origin, the Court delegated it to the General Assembly as that was issue concerning the protection of human rights. Furthermore, the Court advised the Member States to co-operate with the United Nations to complete the decolonisation of Mauritius.


The Court’s appraisal of the United Kingdom’s actions in separating the Chagos Archipelago from Mauritius in 1965 is a noteworthy aspect of the Chagos Advisory Opinion. The inhabitants of the Chagos Islands, who were forcibly evicted from their homes to make way for a US military facility, suffered substantial losses because of that separation. The forced removal of the Chagossians has been widely criticized as a violation of their human rights, and many Chagossians have been fighting for the right to return to their homeland ever since. The Court’s assessment stressed the implications of the United Kingdom’s actions for human rights and emphasised the significance of safeguarding impacted populations’ rights during decolonization processes. However, the Court’s reticence to rule on their human rights has been considered quite disappointing, considering the General Assembly’s static light-touch approach in such matters.

Furthermore, as it was issued within the Court’s advisory jurisdiction, which practically speaking is not at all binding, the Chagos advisory opinion is unenforceable against States. Thus, the United Kingdom has the freedom to disregard the obligations brought forth by the Court’s recognition of right to self-determination of Chagossian people. However, the advisory opinion carries a lot of political and moral weight and can be used to exert pressure on the United Kingdom to uphold its duties.

Besides, the ICJ’s findings in the Chagos Advisory Opinion are likely to be influential in future ICJ decisions on similar issues. Additionally, the advisory opinion can be cited as a source of international law and can be used to support legal arguments in other fora. Therefore, while this decision may not have created any immediate legally enforceable outcomes, its jurisprudence is still relevant and important for future international legal developments.

Moreover, in what can be called a major reversal of its position on the issue, the United Kingdom started negotiations with Mauritius in late 2022 on the “handover” of the territory. Although this has been hailed by some as a positive and encouraging step, there have been many reservations over the same by Chagossians themselves, who believe that not involving them in such negotiations is a repetition of historical mistakes. One thing which is constant, however, is the fact that United Kingdom will guarantee the “safety” of the US military base in Diego Garcia by seeking rights over the same throughout the negotiations. If the negotiations are successful, then the former inhabitants of Chagos, who were forcibly displaced by the United Kingdom, will be allowed to return to their place. Here, the need arises to create a distinction between the interests of Mauritius in general and that of the Chagossians, which are closely aligned but not completely identical.