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

Xinyi ZhangZhongxiu Shen^*

• Zhejiang Normal University, Jinhua, China

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 the 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 towards completing decolonisation and paving the way for the return of the Chagos islanders to their homeland. The imperfection of the agreement is that Mauritius authorises 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 Defence of the British Indian Ocean Territory with the United States, using it as a site for military bases 2 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 the British and America.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.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 status 4 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 Chagosfoot_0 and concluded that Britain had an obligation to bring an end to its administration of the Chagos as rapidly as possible.foot_1 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.foot_2 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 six months. 10 Mauritius coordinated with Non-Aligned Movement and Global South states to amplify its voice, demonstrating how small powers can effectively mobilize collective diplomacy.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. 11 This public opinion warfare, though not an official dispute resolution mechanism, reinforced Mauritius' position by shaping international narratives and moral judgment.The agreement marks the formal end of the British colonial era in Africa and sets an example for the decolonisation of the Global South. Moreover, the event has great anticipated impacts on Small Powers and Great Powers.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.The UK has come under increasing international pressure to hand over control of the archipelago after various United Nations bodies, including its top court and general assembly, sided with Mauritian sovereignty claims in recent years. 12 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 behaviour 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. 13 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 pressures 14 and general considerations of British internal policy, 15 Britain's move inevitably serves as a model for other major powers. The pressure on some Western States 16 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.Diego Garcia remains under 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 towards 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. 17 Earlier this year, Foreign Secretary David Lammy said the deal would not go ahead if the U.S. president had objections. 18 Currently Trump has indicated he would be prepared to back UK's Chagos deal, 19 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. 20 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, 21 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.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 the United Kingdom 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 US, 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 favour 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 US and Britain may use their veto power, a public debate could further expose the violation of the principle of decolonisation by Britain and the US 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 the UK 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 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.Mauritius' campaign for sovereignty over the Chagos Archipelago exemplifies how small states 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 countries 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. 22 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, 23 Mauritius still needs to push for the revision and eventual implementation of the agreement through a pluralistic approach. Perhaps the end of colonial