Restoring Sovereignty? As Brexit Looms, UK Finds Itself at the Heart of Several Self-Determination Controversies

Chloe Roddy
Vol. 40 Associate Editor

In the run-up to the 2016 referendum, pro-Brexit campaigners rallied supporters with assertions of the need to restore the sovereignty of the British Parliament in the face of European “tyranny.”[1] The need for such a demand aside, the UK’s position on its own sovereignty stands in stark contrast to how the former colonial power has policed the right of self-determination in the Chagos archipelago and in Ireland.

The status of the Chagos archipelago has been subject to legal dispute for decades.[2] Mauritius has argued that the agreement it entered into with the British government to detach the Chagos archipelago from its territory was a result of duress.[3] The dispute has its origins in the UK’s independence negotiations with Mauritius in the mid-1960s. In the midst of those talks, the UK entered into formal discussions with the U.S. for the latter’s acquisition of an island on the archipelago to use as a military base.[4] Soon afterward, in the Lancaster House agreement of September 1965, the UK officially split the Chagos Islands from Mauritius.[5] In exchange, Mauritius received a sum of £3 million, fishing and marine resource exploitation rights, and a promise to return the archipelago once the need for military facilities there no longer existed.[6] The UK still controls the archipelago today as a part of the British Indian Ocean Territory (BIOT), a new colony it established following the agreement.[7]

In 1966, the UK reached an agreement with the US for establishment on Diego Garcia, the archipelago’s largest atoll, of what would become one of its two critical military bases in the Asia Pacific region.[8] Pursuant to that agreement, the UK prevented the îlois – the indigenous peoples of the Chagos archipelago who had left the islands – from returning, and forcibly removed all those remaining by 1973.[9] Ever since their eviction, the îlois have been fighting for their right to return home. They remain dispersed in several countries, including the UK, Mauritius and Seychelles.

In June 2017, the United Nations General Assembly (UNGA) voted to ask the International Court of Justice (ICJ) to rule on the legitimacy of the UK’s separation of the Chagos archipelago from the then-territory of Mauritius in 1965.[10]  Mauritius gained independence in 1968 and has fiercely contested the UK’s claim to sovereignty over the archipelago for decades.[11] On February 25 of this year, the ICJ delivered a near-unanimous advisory opinion determining that the UK acted illegally when it imposed territorial controls on the Chagos archipelago without Mauritius’ consent.[12]

The ICJ’s recent decision focuses on the wrongful split of Chagos and retention of the islands under British control. In it, the Court first concluded that the UK’s detachment of the Chagos archipelago from Mauritius was contrary to the right of self-determination and that therefore the decolonization of the territory was not lawfully completed.[13] Second, the Court determined that as a result, the UK’s continuing administration of the archipelago is unlawful and that it is under an obligation to terminate its administration of the archipelago as quickly as possible.[14]

The situation recalls the partition of Ireland in 1920, which the UK accomplished via the Government of Ireland Act 1920. Although the timelines differ – the people of Mauritius voted on independence prior to the severing of the Chagos archipelago, whereas the Irish did so before Britain took control of the Six Counties – both involved the creation of an artificial government entity that remained a part of the UK at a time when each respective territory’s independence loomed on the horizon. In addition, both Mauritius and the Republic of Ireland have pointed to the coercive nature of bargaining talks, and Ireland has consistently denied the legality of the Anglo-Irish Treaty of 1921.[15]

The treaty’s excision of Northern Ireland from what had historically been a single nation provided the impetus for the bloody conflict known as the Troubles in the latter half of the 20th century.[16] The Belfast Agreement brought an end to the Troubles, setting up new cross-border institutions and creating the structure for a new type of devolved government in Northern Ireland. Moreover, the agreement provided that if a majority of voters in a Northern Ireland referendum supported reunification of Ireland, this wish would be respected. However, the power to call such a “border poll” rests solely with a British official, the Secretary of State for Northern Ireland. If at any time it appears “likely” to the Secretary that a majority would vote in favor of reunification, she must exercise such power.[17] Despite Northern Irish views toward reunification seemingly gaining more and more strength in the wake of an impending but undefined Brexit,[18] Secretary Karen Bradley stated earlier this year that the requisite conditions to call a border poll had not been met.[19]

Even though the Belfast Agreement was legitimized through its approval by voters across the Irish Isle, the foundation upon which it rests – the initial partitioning of Ireland which allowed the UK to retain hold of the Six Counties – raises similar questions to those that were raised in the Chagos dispute. Namely, was Ireland ever fully decolonized? If not, is the UK’s ultimate claim to sovereignty over Northern Ireland in contravention of customary international law, devolution notwithstanding? Furthermore, despite the indication in the Belfast Agreement that the UK will recognize the will of the Irish people to reunify, is the conditional nature of Ireland’s exercise of the right of self-determination[20] contrary to that right in the first place?

Although the ICJ’s Chagos archipelago opinion does not create binding law, the UK should take the Court’s decision seriously and take corrective action to bring itself into compliance with international norms. The Brexit negotiations might be occupying much of the country’s collective consciousness, but it is for that very reason that the issue of others’ right to self-determination should not be ignored.


[1] Fintan O’Toole, It Was Never About Europe. Brexit is Britain’s Reckoning With Itself, The Guardian (Jan. 18, 2019), https://www.theguardian.com/commentisfree/2019/jan/18/europe-brexit-britain-state-politics-fit-for-purpose.

[2] Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, Advisory Opinion, ¶¶ 38-53 (Feb. 25, 2019), https://www.icj-cij.org/en/case/169 [hereinafter “ICJ Chagos Decision”]..¶ 38-5353 delines under R21.5.1wed s so recent, it’rns

[3] Id. ¶¶ 43, 103-07. Prior to Mauritius consenting to detachment, the UK Foreign Secretary and the Defense Secretary took the position that if Mauritius would not agree, they would have to resort to “forcible detachment and compensation paid into a fund.” See also Owen Bowcott, UK Used Secret Threats to Keep Chagos Islands, Court Hears, The Guardian (Sept. 3, 2018), https://www.theguardian.com/world/2018/sep/03/mauritius-takes-uk-to-court-over-chagos-islands-sovereignty.

[4] ICJ Chagos Decision, ¶ 94.

[5] Id. ¶¶ 108-12.

[6] Stephen Allen, The Chagos Islanders and International Law 88 (2014).

[7] In addition to the Chagos archipelago, BIOT initially also contained the islands of Aldabra, Farquhar, and Desroches, which had been detached from the Seychelles as a part of the Lancaster House agreement of September 1965. These three islands were returned to Seychelles after it attained independence in 1976, leaving BIOT to consist only of the six main island groups comprising the Chagos archipelago.

[8] Exchange of notes constituting an agreement concerning the availability for defense purposes of the British Indian Ocean Territory, U.K.-U.S., Dec. 30, 1966, 603 U.N.T.S. 273. Due to the UK’s ‘special relationship’ with the U.S., this “exchange of notes” constituted an agreement but did not require British parliamentary approval. The UK leased Diego Garcia to the U.S. for 50 years.in A. Res. 1514 (XV) (Dec. 14, 1960).

[9] The U.S. had demanded “exclusive control” of the island, “without local inhabitants.” David Vine, The Truth About Diego Garcia, Le Monde Diplomatique (Jun. 15, 2015), https://mondediplo.com/openpage/the-truth-about-diego-garcia. With respect to the relocation of the Chagossians, one British undersecretary commented in 1966 that “[t]here will be no indigenous population except seagulls.” Brett Wilkins, UN Court Calls on Britain to ‘Decolonize’ Chagos Islands, Intercontinental Cry (Feb. 27, 2019), https://intercontinentalcry.org/un-court-calls-on-britain-to-decolonize-chagos-islands/. in A. Res. 1514 (XV) (Dec. 14, 1960).

[10] Chagos Legal Dispute Sent to International Court by UN, B.B.C. (Jun. 22, 2017), https://www.bbc.com/news/uk-40376673.

[11] Stefan Donnelly & Tom Laszlo Guha, Fifty Years of Fighting for a Better Future, U.N.A.-U.K. Magazine (Oct. 22, 2018), https://www.una.org.uk/magazine/2018-1/fifty-years-fighting-better-future.

[12] Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, Advisory Opinion (Feb. 25, 2019), https://www.icj-cij.org/en/case/169 [hereinafter “ICJ Chagos Decision”].

[13] ICJ Chagos Decision, ¶¶ 139-74.

[14] Id. ¶¶ 175-82.

[15] Richard J. Harvey, The Right of the People of the Whole of Ireland to Self-Determination, Sovereignty, and Independence, 11 N.Y.L. Sch. J. Int’l & Comp. L. 167, 172 (1990) (noting that Ireland has claimed that the UK threatened “immediate and terrible war” if it did not agree to the terms of the treaty).

[16] See id.

[17] Northern Ireland Act 1998, Sched. 1 [2].

[18] See, e.g., Allan Preston, Poll: Northern Ireland Voters Will Back United Ireland After Brexit, Belfast Telegraph (Sept. 3, 2018), https://www.belfasttelegraph.co.uk/news/northern-ireland/poll-northern-ireland-voters-will-back-united-ireland-after-brexit-37275256.html; Benjamin Mueller, How a ‘No-Deal’ Brexit Could Open a Path to Irish Unity, N.Y. Times (Feb. 15, 2019), https://www.nytimes.com/2019/02/15/world/europe/brexit-northern-ireland.html.

[19] Nick Eardley, Brexit: ‘Very Real’ Chance of Irish Unity Poll if No Deal, B.B.C. (Feb. 8, 2019), https://www.bbc.com/news/uk-politics-47170711.

[20] As enunciated in an influential UNGA resolution from which the British government did not dissent, the right is that of people “freely to determine, without external interference, their political status and to pursue their economic, social and cultural development.” G.A. Res. 2625 (XXV), Declaration on Principles of International Law concerning Friendly Relations and Co-operation among States in accordance with the Charter of the United Nations (Oct. 24, 1970).

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