On February 25, 2019, the International Court of Justice (ICJ) delivered an advisory opinion on the Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965.  The advisory opinion had been requested of the court through a General Assembly resolution in 2017, on the following legal question:

“(a) 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, including obligations reflected in General Assembly resolutions 1514 (XV) of 14 December 1960, 2066 (XX) of 16 December 1965, 2232 (XXI) of 20 December 1966 and 2357 (XXII) of 19 December 1967?;
(b) What are the consequences under international law, including obligations reflected in the above-mentioned resolutions, 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?”

ICJ answered the first question in the negative, and concluded that the decolonization process of Mauritius had not been lawfully completed at the time of Mauritian independence.  And the court held, on the second question, that the United Kingdom was under an obligation to bring to end its administration of the islands as rapidly as possible.  This post will provide a brief factual background regarding the Chagos Archipelago, as well as a succinct legal analysis of the world court’s reasoning and ultimate conclusions.

Where is the Chagos Archipelago and what was its relationship to the United Kingdom and Mauritius prior to Mauritian independence in 1968? Between 1814 and 1965, the Chagos Archipelago was administered by the United Kingdom as a dependency of the colony of Mauritius.  In 1964, during a time when the  United Kingdom was contemplating decolonizing Mauritius, the United States expressed an interest (to the United Kingdom) in establishing a military base on one of Chagossian islands, Diego Garcia.  In 1965, the United Kingdom concluded the co-called Lancaster Agreement with the representatives of the colony of Mauritius.  Through the Lancaster Agreement, the U.K. and Mauritius “agreed in principle to the detachment of the Chagos Archipelago from the territory of Mauritius. This agreement in principle was given on condition that the archipelago could not be ceded to any third party and would be returned to Mauritius at a later date, a condition which was accepted at the time by the United Kingdom.” (para. 171).  After this Agreement, the United Kingdom detached the Chagos Archipelago from Mauritius.  In 1965, the United Kingdom also concluded an agreement with the United States, allowing the latter to build a military base on Diego Garcia.  By 1971, all of the inhabitants of Diego Garcia were forced to relocate from the island by the United Kingdom authorities and the United States proceeded to build a military base on the island.  Mauritius (without Chagos Islands) obtained independence from the United Kingdom in 1968; according to a former Mauritian Prime Minister, Mauritius had no choice but to agree to the detachment of the Chagos Archipelago prior to independence.  As of today, the United States still operates a military base in Diego Garcia (the U.S. – U.K. agreement of 1965, allowing the U.S. to operate a military base in Diego Garcia, has been extended).  The Chagossians have been dispersed, since the early 1970s, in Mauritius, the Seychelles, and the United Kingdom.  By virtue of U.K. law, they have not been allowed to return to the Chagos Archipelago.

How did the ICJ reason in this advisory opinion, and how did it reach its ultimate conclusions? First, the ICJ held that it had jurisdiction over the dispute because the request from the General Assembly for this advisory opinion constituted a “legal question” pursuant to article 65 of the court’s statute (para. 58).  Second, the ICJ held that, in its discretion, it should not decline to exercise jurisdiction over this case.  The court reasoned that it had enough factual information to answer the legal questions asked (paras. 69-74), that it was not for the court to decline jurisdiction based on the argument that the court’s opinion would not assist the General Assembly, as this is for the General Assembly itself to decide (paras.  75-78), and that it was not precluded through the principles of res judicata from rendering this advisory opinion (because the U.K. and Mauritius had arbitrated a slightly different dispute before an arbitral tribunal, and because the U.K. and Mauritius are not the same parties in the present request for an advisory opinion) (paras.  79-80).  Moreover, the ICJ rejected the argument that it should decline jurisdiction because the request for an advisory opinion would force the court to settle a territorial dispute between two states, the U.K. and Mauritius, which had not both consented to the court’s jurisdiction over this dispute (paras. 83-91).  Instead, the ICJ held that “the purpose of the request is for the General Assembly to receive the Court’s assistance so that it may be guided in the discharge of its functions relating to the decolonization of Mauritius.” (para.  86).

After answering the jurisdictional challenges, the ICJ turned to the merits.  The court examined the right to self-determination under customary law, and whether this right existed under customary law in the late 1960s, at the time that the U.K. decolonized Mauritius.  According to the ICJ, General Assembly Resolution 1514 of 1960 “represents a defining moment in the consolidation of State practice on decolonization” (para. 150) and “[t]he wording used in resolution 1514 (XV) has a normative character, in so far as it affirms that ‘[a]ll peoples have the right to self-determination.'” (para. 153).  Moreover, according to the court, “[b]oth 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.” (para. 160).  Thus, the ICJ concluded that the right of self-determination was a part of customary law in 1968, at the time of Mauritian independence.  Next, the court concluded that the people of Mauritius, through the Lancaster Agreement of 1965, did not freely consent to the detachment of the Chagos Archipelago (para. 172), and that the decolonization of Mauritius was thus not lawfully completed, as it did not respect the relevant principles of self-determination.  In light of this conclusion, the court found that “the United Kingdom’s continued administration of the Chagos Archipelago constitutes a wrongful act entailing the international responsibility of that State” (para. 177) and that “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” (para. 178).  Moreover, the ICJ concluded that because “respect for the right to self-determination is an obligation erga omnes, all States have a legal interest in protecting that right” and “while it is for the General Assembly to pronounce on the modalities required to ensure the completion of the decolonization of Mauritius, all Member States must co-operate with the United Nations to put those modalities into effect” (para. 180).

Why did the court (likely) decide the way it did, and what does this all mean? First, it is important to note that the court’s decision was virtually unanimous: the judges unanimously determined that the court had jurisdiction; by twelve votes to two, the judges decided to comply with the request to render the advisory opinion (Judges Tomka and Donoghue against); by thirteen votes to one, the judges reached their substantive conclusions (Judge Donoghue against).  Second, as Marko Milanovic has argued, the outcome of this case may demonstrate how important the framing of the legal question is (“by avoiding the use of the term ‘sovereignty’, Mauritius and the GA defused the likelihood of the Court dismissing the case as involving a bilateral dispute”).  This may explain, in part, why the ICJ judges ultimately reached the conclusions above – that the narrow and clever wording of the advisory opinion request allowed the ICJ to reach particular legal conclusions without having to address issues of U.K. and/or Mauritian sovereignty.  Third, I agree with Marko Milanovic that the ICJ’s discussion of the most fundamental and difficult issue – whether the right of self-determination was part of customary law in 1968, at the time of Mauritian decolonization – was too brief, too rushed, and insufficiently developed in terms of legal analysis.  Fourth, the ICJ did not explain how the people of Mauritius could have freely exercised their right to self-determination (when they consented to the separation of the Chagos Archipelago): was the U.K. at an obligation to conduct a popular referendum in Mauritius on this issue, or were there other modalities of self-determination available in 1968? Fifth, it is clear that this outcome is a big loss for the U.K., as the ICJ most clearly stated that the Mauritian decolonization was not lawfully completed and that the U.K. was under an obligation to end its administration of the Chagos Archipelago immediately. Sixth, it may be argued that the outcome of this case is a loss for other countries, such as the U.S., as the ICJ concluded that all states were under an obligation to co-operate with the United Nations to ensure the completion of the decolonization of Mauritius (does this mean that the U.S. is now under an obligation to dismantle its military base on Diego Garcia?) Seventh, it may also be argued that the ICJ missed another opportunity to pronounce itself on the contours of the right of self-determination, like in the Kosovo Advisory Opinion.  The legal question in this advisory opinion concerned the right to self-determination directly; instead of quickly concluding that the right was part of customary law in 1968, the court could have included a more detailed legal analysis of the content and modalities of the right of self-determination under customary law.

It remains to be seen how the U.K. (or the U.S.) will react to this advisory opinion, whether the U.S. will be willing to negotiate the relocation of its military base in Diego Garcia, and whether the people of the Chagos Arhipelago may be allowed to return to their home land.