Mauritius' policy toward sovereignty over the Chagos Archipelago: a pluralistic approach to international dispute settlement

With the continuous attention of the international community, Britain finally agreed on October 3, 2024, to return the sovereignty of the Chagos Archipelago to Mauritius after long-term mediation and efforts. Mauritius has adopted a pluralistic approach to international dispute resolution in its quest for sovereignty over the Chagos Archipelago, which is likely to have expected implications for Small Powers and Great Powers. In addition to anticipating these impacts, this policy brief provides actionable recommendations on how Mauritius can facilitate the through implementation of the agreement in the interests of the Chagos Islanders.

1 Introduction

As reported on October 3, 2024, the governments of the Republic of Mauritius and Britain gave an agreement on the Chagos Archipelago (hereinafter referred to as the Chagos), agreeing that Mauritius is sovereign over the Chagos. Mauritius can implement a resettlement programme for the Chagos former islanders, except Diego Garcia, and Britain will support those through measures such as the establishment of a trust fund. In addition, Britain and Mauritius will strengthen economic security and environmental partnership building and work together to protect the ecology of the Chagos. Mauritius has seen this agreement as an important step toward completing decolonization and paving the way for the return of the Chagos islanders to their homeland. The imperfection of the agreement is that Mauritius authorizes Britain to exercise the sovereign rights and authorities of Mauritius over Diego Garcia, the largest island in the Chagos, for an initial period of 99 years.¹ The Chagos were administered by Britain from 1814 to 1965 as a dependency of the colony of Mauritius. In 1965, the Prime Minister of Mauritius agreed the Chagos being separated from Mauritius. On 8 November 1965, Britain established a new colony consisting of the Chagos and other islands, and on 30 December 1966 concluded the Agreement Concerning the Defense of the British Indian Ocean Territory with the United States, using it as a site for military bases² and forcibly expelling the Chagos Islanders. After that, the United States built a military base on Diego Garcia.

This policy brief analyses the range of policies that Mauritius pursued in its quest for sovereignty over the Chagos prior to the agreement between the two countries, predicts the impacts that these policies would have had on Small Powers and Great Powers respectively, and proposes actionable recommendations for Mauritius to genuinely reclaim sovereignty over the Chagos from Britain and the United States.

2 The strategy behind Mauritius' sovereign policy

Mauritius pursed a multi-pronged approach to regain sovereignty over the Chagos. This included legal action, diplomatic engagement, and strategic communication efforts aimed at building international support and applying pressure on Britain.

2.1 Legal and constitutional foundations

Mauritius codified the Chagos as part of its national territory within its Constitution.³ It supported legal action in regional and international forums, notably backing the Chagos Islanders' case at the European Court of Human Rights. While the Court declined to take up the case on the grounds that the applicants did not have proper victim status⁴ and had not been deprived of the benefit of a final and enforceable decision,⁵ Mauritius persisted in seeking legal clarity through other means. In 2017, responding to Mauritius' diplomatic lobbying, the UN General Assembly (hereafter referred to as the UNGA) requested an advisory opinion from the International Court of Justice (hereafter referred to as the ICJ) on the legal consequences of the separation of the Chagos from Mauritius in 1965.⁶ In 2019, the ICJ stated in its advisory opinion that Britain imposed an unlawful detachment on the Chagos⁷ and concluded that Britain had an obligation to bring an end to its administration of the Chagos as rapidly as possible.⁸

2.2 Diplomatic advocacy and coalition-building

Mauritius engaged extensively with multilateral organizations. Within the African Union (hereafter referred to as the AU), it issued a condemnation of the British occupation of the Chagos and demanded that it comply with international law (African Lii, 2019). At the UN, it led a diplomatic campaign culminating in the 2019 UNGA resolution, adopted by an overwhelming majority, demanding the British unconditional withdrawal within 6 months (United Nations, 2019). Mauritius coordinated with Non-Aligned Movement and Global South states to amplify its voice, demonstrating how small powers can effectively mobilize collective diplomacy.

2.3 Strategic communication and public engagement

Beyond formal diplomacy, Mauritius actively campaigned in the public sphere. It framed the Chagos dispute as a decolonization issue, garnering media attention and leveraging civil society networks to sway global opinion.⁹ This public opinion warfare, though not an official dispute resolution mechanism, reinforced Mauritius' position by shaping international narratives and moral judgment.

3 Anticipated impacts of Mauritius' strategy

The agreement marks the formal end of the British colonial era in Africa and sets an example for the decolonization of the Global South. Moreover, the event has great anticipated impacts on Small Powers and Great Powers.

3.1 Impact on small powers: emphasis on the concurrent use of multiple dispute resolution methods

Mauritius' success provides a model for small powers. Firstly, it reinforces the role of legal norms in empowering postcolonial claims and encourages small powers to persist in asserting sovereignty despite power asymmetries. Secondly, the event shows that while the ICJ and international institutions can legitimize claims, diplomacy and public advocacy are essential for implementation. Thirdly, by employing all available mechanisms concurrently, small powers can multiply their leverage and resilience. To be specific, it was difficult to deal with the growing complexity of international disputes through legislative and judicial means alone. Mauritius has resorted to various means of dispute settlement, including diplomatic and political, while turning to international dispute resolution institutions such as the UNGA and the ICJ. The advisory opinion of the ICJ and the resolutions of the UNGA had laid a good foundation for the settlement of the dispute, and it was the combination of those methods and Mauritius' diplomatic and political means that had led to the current outcome.

3.2 Impact on great powers: increase external pressure for non-compliance with the international rule of law

Britain has come under increasing international pressure to hand over control of the Chagos after various United Nations bodies, including its top court and general assembly, sided with Mauritian sovereignty claims in recent years (Lucy Clarke-Billings, 2025b). Britain, as a great power, complied with the ICJ advisory opinion and the UNGA resolution in this event in accordance with the United Nations Charter (hereinafter referred to as the UN Charter) and the principles of international law. This behavior not only demonstrates the British sense of national responsibility and enhances the British influence in the international arena, but also provides a model for other great powers to comply with the international rule of law and assume responsibility for their international legal obligations. Great powers, while not legally privileged under the principle of sovereign equality, often recognize a moral obligation to uphold international law. This obligation stems from their self-perceived role as global leaders and the substantial influence they wield on the international stage.

Even if a great power is not considered to be legally privileged under the principle of sovereign equality, the great power does not deny that it should still assume special obligations in the absence of legal privilege, one of the bases—in the view of the great power, or even the main basis—is the great power's moral perception of its own national identity, that being a great power should bear special obligations to the international community or to other states. By virtue of the substantial benefits they receive and their great capacity to act, great powers should be under a heavier obligation to observe the international rule of law and international rules than small powers. Although the reasons for Britain's relinquishment of sovereignty over the Chagos are manifold, including legal and diplomatic political pressures¹⁰ and general considerations of British internal policy,¹¹ Britain's move inevitably serves as a model for other major powers. The pressure on some Western States¹² to abide by the international rule of law and pay attention to the advisory opinions of the ICJ and the resolutions of the UNGA in international dispute issues such as territory and human rights has increased, limiting the abuse of the prerogatives as a major power, and reinforcing the legal and political obligations of major powers to abide by the international rule of law.

4 The role of the United States and strategic trade-offs

Diego Garcia remains under the United States military control, making American interests central to the future of the agreement. With the involvement of the United States, the process of subsequent refinement and implementation of the agreement on the return of sovereignty over the Chagos to Mauritius will be significantly affected. Notably, progress toward an agreement has also been delayed after the election of Donald Trump because negotiators wanted to give the new U.S. administration time to examine the details of the plan (Whannel, 2025). Earlier this year, Foreign Secretary David Lammy said the deal would not go ahead if the U.S. president had objections (Congyan, 2012). Currently Trump has indicated he would be prepared to back UK's Chagos deal (Lucy Clarke-Billings, 2025a), mainly due to the facts that the Chagos deal guarantees the continuity of U.S. operations and reaffirms Diego Garcia's enduring role as a linchpin of American strategy in the Indian Ocean (Kumar, 2025). Against this background, it is likely that this agreement to fully recover sovereignty over the Chagos, including Diego Garcia, will be frustrated when the details of a subsequent treaty are agreed upon. Obviously, the United States will not give up its military bases on Diego Garcia easily. However, in order to maintain relations with Mauritius and safeguard the United States' military superiority over China in the Indian Ocean, the United States may make a balance between sovereignty claims and strategic choices (see text footnote 10), continuing backing symbolic restitution to Mauritius while resisting full sovereignty transfer over Diego Garcia, which reflects a balancing act between upholding postcolonial justice and preserving geostrategic supremacy.

5 Actionable recommendations: leveraging the power of great powers to balance the obstruction of Britain and the United States

The efforts of Mauritius in the sovereignty dispute over the Chagos are an example of a small power using international law, multilateral diplomacy and the public opinion warfare to confront the great power. However, given the deep-rooted military and geopolitical interests of Britain and the United States, it would be difficult to force them to hand over sovereignty through international moral and judicial victories alone. Therefore, the final solution will still depend on the political games and compromises of the great powers. In order to enhance the pressure on Britain and the United States, Mauritius can adopt the following strategies to gradually change the power balance by enlisting the support of other major powers:

• Elevate the issue to the UN Security Council. Despite the overwhelming majority in favor of Mauritius in the UNGA in 2019, the Security Council is the body that can make binding resolutions. Mauritius can join forces with African, ASEAN and Non-Aligned countries to ask the Security Council to consider the Chagos issue, invoking Article 73 of the UN Charter (Obligations of Non-Self-Governing Territories) and the Advisory Opinion of the ICJ. Although the United States and Britain may use their veto power, a public debate could further expose the violation of the principle of decolonization by Britain and the United States and force the two countries into a passive position in international public opinion.

• Build Strategic Coalitions with Caution. Mauritius needs to build a wider ‘anti-colonial coalition', focusing on gaining influential countries such as India and South Africa. Taking the African Union as an example, Mauritius can push AU member states to impose symbolic sanctions (e.g., limiting high-level visits) on Britain to intensify collective pressure. However, Great Powers like India and South Africa may be reluctant to jeopardize their economic and security ties with Britain and the United States. To overcome this, Mauritius should emphasize the shared principles of decolonization and territorial integrity, framing the issue as a matter of global justice rather than narrow self-interest.

• Exchanging maritime economic cooperation for support from major powers. The fisheries, potential oil and gas resources in the waters around the Chagos are of economic value, and Mauritius can use the right to exploit these resources as a bargaining chip to attract the cooperation of major powers such as China, India and South Africa as mentioned, as incentives for strategic partnerships, offering mutually beneficial cooperation agreements in exchange for political support.

6 Conclusion

Mauritius' campaign for sovereignty over the Chagos exemplifies how small powers can effectively challenge global power structures through pluralistic, coordinated strategies. While legal victories matter, their real-world impact depends on diplomatic follow-through, public engagement, and geopolitical navigation. For other small powers entangled in territorial or sovereignty disputes, Mauritius' approach offers a replicable model: blend litigation with negotiation, moral arguments with legal claims, and coalition-building with strategic communication. In a world where the international rule of law is often selectively applied, consistent, diversified, and principled advocacy remains a powerful tool for small powers.

On 22 May 2025, Britain and Mauritius signed a bilateral agreement to return sovereignty over the Chagos. It seemed a superficial success, with two remaining questions, one is the foreign military presence on Diego Garcia, another one is the rights of Chagos Islanders. For the Chagos Islanders the demands remain unchanged—they seek the right to return, financial reparations and recognition of the injustices they have endured (Lemauricien, 2025). Thus, while some of the British have shown a desire to help the Chagos Islanders and to correct Britain's mistakes as a post-colonial power (Caldwell, 2019), Mauritius still needs to push for the revision and eventual implementation of the agreement through a pluralistic approach. Perhaps the end of colonial history in Africa will be reached by the united non-colonial countries. Let's see.

Author contributions

XZ: Writing – original draft, Writing – review & editing. ZS: Writing – original draft, Writing – review & editing.

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The author(s) declare that no financial support was received for the research and/or publication of this article.

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Footnotes

1. ^“UK and Mauritius joint statement,” Foreign, Commonwealth & Development Office, Prime Minister's Office, 10 Downing Street and The Rt Hon Sir Keir Starmer KCB KC MP, 3 October, 2024, https://www.gov.uk/government/news/joint-statement-between-uk-and-mauritius-3-october-2024.

2. ^Advisory opinion of the International court of Justice on the legal consequences of the separation of the Chagos Archipelago from Mauritius in 1965, 25 February 2019, the para.27, p.107.

3. ^Constitution of Mauritius, Article 111, 1968.

4. ^Chagos Islanders v. the United Kingdom, ECHR, Application no.35622/04, 11 December 2012.

5. ^Chagos Islanders v. the United Kingdom, ECHR, Application no.35622/04, 11 December 2012, para. 85, p. 25.

6. ^Request for an advisory opinion of the International Court of Justice on the legal consequences of the separation of the Chagos Archipelago from Mauritius in 1965, the United Nations General Assembly, A/71/142, 14 July 2016.

7. ^Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, the International Court of Justice, para. 174, p. 46, 25 February 2019.

8. ^Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965, the International Court of Justice, para. 182, p. 139, 25 February 2019.

9. ^In 2022, Jagdish Koonjul, the Mauritian ambassador to the United Nations, raised the country's flag on a beach with the group gathered around above the island of Peros Banhos, which was reported by media like The Guardian.

10. ^Mauritius has long maintained in public its claim to sovereignty over the Chagos Archipelago. Following the adoption of a resolution by the United Nations General Assembly on 22 May 2019, spokenmen from the United Kingdom and Mauritius engaged in a heated debate on the floor of the UN General Assembly.

11. ^After Britain's Labour Party won the 2022 general election, Starmer, the new prime minister, made resolving the Chagos Archipelago issue a priority.

12. ^Nicaragua v. United States of America, the International Court of Justice, Judgement, 27 June 1986. In 1986, in the case Nicaragua v. United States, the United States set a famous precedent of opposing the jurisdiction of international judicial bodies and refusing to comply with international judicial judgements. The case concerned military and paramilitary activities carried out by the United States in Nicaragua with the intention of destabilizing the Government of Nicaragua. The United States objected to the jurisdiction of the International Court of Justice during the jurisdictional phase of the trial and, in October 1985, the compulsory jurisdiction of the Court over the United States was lifted. The International Court of Justice tried the United States in absentia and ultimately ruled against the United States. Since then, the United States has refused to recognize and implement this judgment of the International Court of Justice.

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