On 25 February 2019, the International Court of Justice (hereinafter ICJ or Court) delivered its advisory opinion on the Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965 (hereinafter Chagos Archipelagos Opinion or Opinion). Adopted on request of the UN General Assembly, the opinion recognises that ‘the process of decolonization of Mauritius was not lawfully completed when that country acceded to independence’ and, as a consequence, that ‘the United Kingdom is under an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible’. The Court was almost unanimous in its position, with 12 judges out of 14 who voted in favour of complying with the General Assembly’s request for an advisory opinion and 13 agreed on the merit of the question.
The Chagos Archipelagos Opinion is the twenty-seventh advisory opinion adopted by the ICJ since its establishment in 1946. The ICJ opinion touches upon a number of interesting legal questions. This post focuses, in particular, on the Court’s analysis of the argument raised by the British Government according to which the General Assembly’s request related to a pending dispute between two states (the Republic of Mauritius and the United Kingdom) and, therefore, was in violation of the established principle of international law that a State is not obliged to allow its disputes to be submitted to judicial settlement without its consent.
1. Historical background
Before looking at the relevant section of the Opinion, it is worth providing a brief overview of the historical background of the case. The question of the legality of the separation of the Chagos Archipelagos from Mauritius has been a point of controversy for many decades. The Archipelagos was detached from the main island in 1965 when Mauritius was still a colony of the British Empire and only a few years prior to the country’s independence. Following the separation, the Chagos Archipelagos – together with a few other islands detached from Seychelles – became part of a new British colony known as the British Indian Ocean Territory (hereinafter “BIOT”). In 1966, the United Kingdom concluded an agreement with the United States giving it permission to convert one of the BIOT’s islands – Diego Garcia – into a US military base. As a consequence, between 1967 and 1973, the entire indigenous population of the Archipelagos (known as Chagossians) was forcibly removed from the territory and prevented from returning.
2. The existence of a bilateral dispute as a compelling reason to deny an advisory opinion
One of the most interesting parts of the opinion concerns the Court’s discussion on whether it should exercise its discretionary power to deny the General Assembly’s request or not. Indeed, Article 65(1) of the ICJ Statute stipulates that the Court ‘may give an advisory opinion … at the request of whatever body may be authorized by or in accordance with the Charter of the United Nations’, leaving to the Court’s discretion the decision of whether to comply with the request or not.
Over the years the Court has provided a clear explanation of the rationale behind this interpretation of Article 65(1) by observing that ‘[t]he discretion whether or not to respond to a request for an advisory opinion exists so as to protect the integrity of the Court’s judicial function as the principal judicial organ of the United Nations’. At the same time, the judges have recognised that such a discretionary power should be exercised by the Court carefully. Indeed, as per consistent jurisprudence, the ICJ has observed that ‘only “compelling reasons” may lead the Court to refuse its opinion in response to a request falling within its jurisdiction’. The determination of what may constitute a ‘compelling reason’ is left to the careful evaluation of the judges on a case-by-case basis.
In the Chagos Archipelagos case, the participants to the proceeding referred to a number of ‘compelling reasons’ to deny the General Assembly’s request.. Among these, the most controversial one concerned the existence of a bilateral dispute (sovereignty over the Chagos Islands) between two States (the United Kingdom and the Republic of Mauritius) ‘which have not consented to the settlement of that dispute by the Court’. It was argued that the request for the Court’s opinion constituted a blatant attempt at ‘circumventing the principle that a State is not obliged to allow its disputes to be submitted to judicial settlement without its consent’.
In its written statement, the United Kingdom observed that, since the 1980s, the Republic of Mauritius has repeatedly contested the legality of the detachment of the Chagos Archipelagos and attempted on multiple occasions to assert its sovereignty claim both bilaterally and internationally. Particular emphasis was put on Mauritius’ attempt to get a formal recognition of its sovereignty over the Archipelagos in the context of the arbitral proceeding commenced under the United Nations Convention on the Law of the Sea (‘UNCLOS’) following the British decision to declare a marine protected area in and around the Chagos Archipelago. According to the United Kingdom, ‘[t]he Chagos Arbitration provides an important illustration of how the Request – despite its formulation … – concerns issues that have long been in dispute between the United Kingdom and Mauritius at the bilateral level’.
The United Kingdom’s position was not shared by the Court. In the opinion, the Court emphasised how the questions posed by the General Assembly did not concern the territorial dispute between the Republic of Mauritius and the United Kingdom but the broader issue of decolonisation and of the exercise of the right to self-determination. In particular, the judges observed that the issues at the core of the General Assembly’s request were to be ‘located in the broader frame of reference of decolonization, including the General Assembly’s role therein, from which those issues are inseparable’. The fact that the Court had to ‘pronounce on legal issues on which divergent views have been expressed by Mauritius and the United Kingdom does not mean that, by replying to the request, the Court is dealing with a bilateral dispute’.
This was not the first time the Court had to determine whether a request for an advisory opinion was indeed a hidden attempt at solving a bilateral dispute by circumventing the requirement of consent in the contentious jurisdiction. The same issue arose in a number of previous cases. In the Western Sahara opinion, in particular, the same argument was raised by the Spanish Government to persuade the Court to exercise its discretionary power to deny an advisory opinion. At the time, the issue at the core of the advisory proceeding was the ongoing process of decolonisation of Western Sahara. Spain argued that the advisory procedure was used by Morocco ‘as an alternative after the failure of an attempt to make use of the contentious jurisdiction with regard to the same question’. In its opinion, the Court firmly rejected Spain’s position by observing that the broader context in which the request has been formulated needed to be taken into consideration. Like in the Chagos Archipelagos Opinion, the Western Sahara case Also, the Court needs to assess whether the opinion may provide assistance to the General Assembly in exercising functions bestowed on it by the UN Charter.
Similarly, in the advisory opinion on the Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, the Court rejected the arguments made by Israel and the United Kingdom concerning the existence of a bilateral dispute between Israel and Palestine. The Court did not deny that opposite views had been expressed by the two states involved. Nonetheless, it observed that ‘[g]iven the powers and responsibilities of the United Nations in questions relating to international peace and security, it is the Court’s view that the construction of the wall must be deemed to be directly of concern to the United Nations’. In other words, the issue at stake went well beyond a mere bilateral dispute.
brief analysis conducted above aimed at highlighting a trend in the Court’s
jurisprudence on the determination of whether a bilateral dispute was indeed at
the core of a request for an advisory opinion and, if so, whether this
justifies a denial from the Court to exercise its advisory jurisdiction. As
observed, the Court has consistently stated that, in determining the actual
purpose of a request for an advisory opinion, strong emphasis needs to be put
on the context in which the request has been made and on whether the opinion
may assist the General Assembly in the exercise of its functions. If, on the one
hand, such an approach allows the Court to express its view on a wider range of
legal issues, on the other, it is undeniable that most bilateral disputes could
be contextualised in a ‘broader frame of reference’, thus arguably partially
eroding the principle of consent by a State to the judicial settlement of its
dispute with another State.
 ICJ, Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, Advisory Opinion (23 February 2019), paras. 174 and 182.
 Ibid., para. 183.
 Ibid., para. 28.
 Ibid., para. 33.
 Ibid., para. 36.
 Ibid., para. 37.
 Ibid., para. 64. See also ICJ, Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Advisory Opinion (9 July 2004), paras. 44-45; ICJ, Accordance with International Law of the Unilateral Declaration of Independence in respect of Kosovo, Advisory Opinion (22 July 2010), para. 29.
 ICJ, Chagos Archipelago, Advisory Opinion (23 February 2019), para. 65. See also ICJ, Construction of a Wall, Advisory Opinion, (9 July 2004), para. 44; ICJ, Kosovo, Advisory Opinion (22 July 2010), para. 30.
 ICJ, Chagos Archipelago, Advisory Opinion (23 February 2019), para. 65.
 Ibid., para. 83.
 Ibid., para. 85.
 ICJ, Chagos Archipelago, Written Statement submitted by the United Kingdom of Great Britain and Northern Ireland (15 February 2018), Chapter V.
 Ibid., Chapter VI.
 Ibid., Chapter VI, para. 6.2.
 ICJ, Chagos Archipelago, Advisory Opinion (25 February 2019), para. 86.
 Ibid., para. 88.
 Ibid., para. 89.
 ICJ, Western Sahara, Advisory Opinion (16 October 1975), para. 34.
 Ibid., para. 27.
 Ibid., para. 38.
 Ibid., para 39.
 ICJ, Construction of a Wall, Advisory Opinion (9 July 2004), para. 48.
 Ibid., para. 49.