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Separation of the Chagos Archipelago from Mauritius

Anmolam ( is a lawyer and runs a non-profit organisation BDLAAAW (Buddies for Legal Aid and Awareness). Farheen Ahmad ( is a PhD candidate in international law at South Asian University, New Delhi.

The judgment of the International Court of Justice in the matter of the legal impact of the separation of the Chagos archipelago from Mauritius is examined. Despite its limitations, this judgment, in the current global atmosphere of protectionism, hyper-nationalism, and fast-diminishing faith in international institutions, has some positive highlights.

The advisory opinion (hereinafter referred as judgment) rendered by the International Court of Justice (ICJ) inLegal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965 has been hailed by many observers as a significant event in the discourse on decolonisation. Not only is it seen as a progressive opinion which reaffirms the right to self-determination, but it also throws light upon the changing political structures in the international legal order. In addition to its legal significance, the judgment also exposes the remnants of colonialism and imperialism that persists. This bolsters the assertion that while

colonialism has largely ended ... imperialism ... lingers where it has always been, in a kind of general cultural sphere as well as in specific political, ideological, economic, and social practices. (Said 1993: 8)

This article is an attempt to peruse the judgment and underline the implications that it may hold for international order in coming years. Broadly, the court opined that the United Kingdom (UK) had separated the Chagos Archipelago from the British colony of Mauritius in contravention of the right to self-determination and thereby the process of decolonisation of Mauritius was not completed in accordance with international law. Before going into the merits of the case, it is imperative to glance over the historical facts that led to the case.

Background of the Controversy

Mauritius and its dependent islands (one of which was the Chagos Archipelago) used to be a colony of the UK till 1968. In 1964, during its deliberations with the UK, the United States (US) expressed its interest to establish a military communication facility on Diego Garcia, the principal island of the Chagos Archipelago. This led to discussions between the UK and the representatives of the colony of Mauritius on the question of the detachment of the Chagos Archipelago from Mauritius. On 23 September 1965, an agreement called “the Lancaster House Agreement” was entered into between the UK and representatives of Mauritius wherein Mauritian representatives agreed in principle to the detachment of the Chagos Archipelago in lieu of,inter alia, a sum of £3 million with the condition that the archipelago would be returned to Mauritius when the need for the military facilities on the islands disappeared. In November 1965, a colony, known as the British Indian Ocean Territory (BIOT) consisting of the Chagos Archipelago, was established by the UK. The US and the UK concluded an agreement for the establishment of a military base by the US on the Chagos Archipelago which also led to the deportation of the inhabitants of Chagos (Chagossians) who were also prevented from returning. On 12 March 1968, Mauritius became an independent state and on 26 April 1968, it was admitted to membership of the United Nations (UN).

In June 2017, in furtherance of Article 96 of the statute of ICJ,1 the General Assembly of the UN adopted a resolution (Resolution 71/292) requesting an advisory opinion from the court.

The resolution sought answers to two questions:

(i) “Was the process of decolonization 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?”

(ii) “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?”

In its judgment, the court first responded to the challenges made to its jurisdiction. The grounds for challenges were: First, advisory proceedings are not suitable for determination of complex and disputed factual issues; second, the court’s response would not assist the General Assembly in the performance of its functions; third, it would be inappropriate for the court to re-examine a question already settled by the Tribunal in the Arbitration regarding the Chagos Marine Protected Area under United Nations Convention on the Law of the Sea (UNCLOS); and fourth, the questions asked in the present proceedings relate to a pending bilateral dispute between two states which have not consented to the settlement of that dispute by the court. After examining these arguments, the court concluded that it had jurisdiction in the case by providing following reasons: first, it had enough material to decide the matter; second, its duty was only to render the opinion; third, this was not a case of res judicata since the issues before it were different from the arbitration tribunal, and, fourth, the issue pertained to decolonisation rather than being a territorial dispute between two states.

The court then moved on to the merits of the case. Briefly, its opinion can be summarised as follows. It first delved into identifying the applicable law pertaining to self-determination for the period between 1965 and 1968. It recalled that, in addition to the purposes of the UN to have respect for the principle of equal rights and self-determination of peoples under Article 1 (2) of the Charter, it also contains provisions that would enable non-self-governing territories ultimately to govern themselves. The court underscored the adoption of resolution 1514 (XV) as a defining moment in “the consolidation of State practice on decolonization” (para 142). It highlighted the declaratory as well as normative character of this Declaration. For the court, the Declaration “has a declaratory character with regard to the right to self-determination as acustomary norm, in view of its content and the conditions of its adoption” (para 15). Moreover, it also crystallises the norm that all peoples have the right to self-determination.

Turning to the inquiry as to whether the detachment of the Chagos Archipelago from Mauritius was carried out in accordance with international law, the court considered the circumstances in which the colony of Mauritius agreed in principle to such a detachment. It found that this detachment was not based on the free and genuine expression of the will of the people concerned. The ICJ determined that owing to the unlawful detachment of the Chagos Archipelago and its incorporation into a new colony, called BIOT, the process of decolonisation of Mauritius was notlawfully completed when Mauritius accomplished independence in 1968 (emphasis added).

On the second question of consequences arising from the continued administration by UK of Chagos, the court only pointed towards the obligation of the UK to bring to an end to its administration of the Chagos Archipelago as swiftly as possible. However, it did not delve into the modalities necessary for ensuring the completion of the decolonization of Mauritius. It left it for the UN General Assembly to see to its culmination in the exercise of its functions relating to decolonisation.

A New Vista?

Two jurisprudential underpinnings of the judgment that attract our attention are the issues of self-determination and unequal treaty. Although there is not an explicit mention of the term “unequal treaty,”2 it may be implied through the court’s understanding of the validity of the Lancaster House Agreement. In the court’s view, 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 UK, was under the authority of the latter. The court is of the view that 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 (para 172). The relevant observation of the court in this regard is that

the circumstances in which the colony of Mauritius agreed in principle to the detachment of the Chagos Archipelago was not based on thefree and genuine expression of the will of the people concerned. (para 172)

Although the Vienna Convention on Law of Treaties3 does not recognise “unequal treaties” as a special legal category, reflection and practice relating to this concept have influenced the development of international law (Anne Peters 2012: 49). To those scholars who argue for the redundancy of the concept of unequal treaties in the 21st century, the case law is a testimony to the uneven and unequal bargaining powers of the states participating in negotiations to any treaty. As Wheaton remarked,

The obligation of treaties, by whatever denomination they may be called, is founded, not merely upon the contract itself, but upon those mutual relations between the two states, which may have induced them to enter into certain engagements. (Wheaton 1880: 39)

The contribution of the discourse on unequal treaties is that it made international legal scholarship more sensitive to the discrepancy between formal equality and substantial political and economic inequality (Anne Peters 2012: 49).

The court’s opinion in the long run is jurisprudentially significant as it ultimately highlights the unequal bargaining positions of the states in the international order. For a just world order, it is important to consider the essence of this argument wherein the court seems to be saying that if the parties are not on equal footing then an agreement cannot be held valid.

The court’s views on the right to self-determination can be viewed as both progressive as well as limited. While the Court has unequivocally upheld the traditional understanding of the right to self-determination as a necessary corollary of the decolonisation process and the right to self-determination as an essential attribute of sovereignty,it may be argued that the case has also exposed the inherent and systemic “state centrism” of international law wherein even the human right of self-determination finds its semblance from the prism of state and not the aspirations of people. It even acknowledged the deplorable condition of the Chagossians. It observed, in Paras 114 and 115, that between 1967 and 1973, the inhabitants of the Chagos Archipelago who had left the islands were prevented from returning. The other inhabitants were forcibly removed and prevented from returning. On 16 April 1971, the BIOT commissioner enacted an Immigration Ordinance, which made it unlawful for any person to enter or remain in the Chagos Archipelago without a permit. Till date, these Chagossians remain scattered in several countries, including the UK. Owing to the laws of the UK and judicial decisions rendered by its courts, they are not allowed to return to the Chagos Archipelago.

On this issue, the court opined that the issue of resettlement on the Chagos Archipelago is an issue relating to the protection of the human rights of those concerned which should be addressed by the General Assembly during the completion of the decolonisation of Mauritius. While the authors appreciate the legal limitations of the court, it can be argued that a more proactive approach could have been adopted. For instance, Judge Trindade in his separate opinion contends that the Chagossians deserve reparations for the hardships they have been made to suffer. The right to self- determination needs a more nuanced analysis in this post colonial era. For instance, as pointed out by the renowned jurist, Ian Brownlie,

This core consists in the right of a community which has a distinct character to have this character reflected in the institutions of government under which it lives. The concept of distinct character depends on a number of criteria which may appear in combination. (1970: 90)

Notwithstanding all the limitations of the judgment, in this global atmosphere of protectionism, hyper-nationalism and dwindling faith in international institutions, this advisory opinion has come as a silver lining. Although ICJ’s advisory opinion does not create law and just declares it, it is expected from the UK, which despite its non-participation, has a responsibility to take necessary actions in compliance with international law, both in letter and spirit.


1 The court has a twofold role: first, to settle legal disputes submitted to it by States, in accordance with international law (its judgments have binding force upon the parties and are without appeal for the parties concerned); and, second, to give advisory opinions, as per Article 96 of the Statute of the ICJ, on legal questions referred to it by duly authorised United Nations organs and agencies of the system.

2 An unequal treaty is characterised by its unequal substance-imbalance of treaty obligations, non-reciprocity, extreme restriction of sovereignty-and/or by the unequal procedure of its conclusion-treaties signed under military, political or economic coercion. It primarily refers to bilateral treaties concluded in the second half of the 19th and beginning of 20th century, mostly between Western and Non-western states.

3 The Vienna Convention on the Law of Treaties is a treaty relating to the secondary rules on treaties between states. It was adopted on 23 May 1969 and entered into force on 27 January 1980.


Brownlie, Ian (1970): “An Essay in the History of the Principle of Self-determination,”Studies in the History of the Law of Nations,Alexandrowicz C H (eds), Dordrecht: Springer.

ICJ (2019): Advisory Opinion, “Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965,” 25 February,International Court of Justice,

Peters, Anne (2012): “Unequal Treaties,”Max Planck Encyclopedia of International Law,Wolfrum (ed), Oxford: OUP.

Said, E (1993):Culture and Imperialism, Random House,Separate Opinion, Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965,

UNTS (1945):Charter of the United Nations, 24 October, 1, United Nations Treaty Series, XVI.

— (1946):Statute of the International Court of Justice, 18 April, 33, United Nations Treaty Series, 993.

(1969):Vienna Convention on the Law of Treaties, 23 May, United Nations Treaty Series, Vol 1155, p 331.

Wheaton, H (1880):Elements of International Law, London: Boyd A Stevens and Sons.

Updated On : 17th Jun, 2019


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