Chagos Archipelago sovereignty dispute

Sovereignty over the Chagos Archipelago is disputed between Mauritius and the United Kingdom. Mauritius has repeatedly claimed the Chagos Archipelago as part of its territory and that the British claim is a violation of United Nations resolutions banning the dismemberment of colonial territories before independence. The UK government has stated that it has no doubt about its sovereignty over the Chagos, yet has also said that the Chagos will be given to Mauritius once the islands are no longer required for military purposes. Given the absence of any progress with the UK, Mauritius took up the matter at various legal and political forums.
Between 1967 and 1973, the entire population of the Chagos Archipelago was either prevented from returning or forcibly removed by the United Kingdom. The main forcible removal of Diego Garcia’s population took place in July and September 1971. On 18 March 2015, the Permanent Court of Arbitration unanimously held that the marine protected area (MPA) which the United Kingdom declared around the Chagos Archipelago in April 2010 was created in violation of international law. The UK had argued that those undertakings were not binding and had no status in international law.
In 22 June 2017, by a margin of 94 to 15 countries, the UN General Assembly asked the International Court of Justice (ICJ) to give an advisory opinion on the separation of the Chagos Archipelago from Mauritius before the country's independence in the 1960s. In September 2018, the International Court of Justice began hearings on the case. 17 countries argued in favour of Mauritius. The UK and its allies argued that this matter should not be decided by the court but should be resolved through bilateral negotiations. On 25 February 2019, the judges of the International Court of Justice by thirteen votes to one stated that the United Kingdom is under an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible. Only the American judge, Joan Donoghue, voted in favor of the UK. The president of the court, Abdulqawi Ahmed Yusuf, said the detachment of the Chagos Archipelago in 1965 from Mauritius had not been based on a "free and genuine expression of the people concerned." "This continued administration constitutes a wrongful act," he said, adding "The UK has an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible and that all member states must co-operate with the United Nations to complete the decolonization of Mauritius."
On 3 November 2022, it was announced that the United Kingdom and Mauritius had decided to begin negotiations on sovereignty over the British Indian Ocean Territory, taking into account the recent international legal proceedings. On 3 October 2024, the UK agreed to hand over the Chagos Islands to Mauritius, although this was controversial given the presence of a U.S. military base on one of the islands. On 1 April 2025, U.S. President Donald Trump approved the deal between the UK and Mauritius.
The Constitution of Mauritius states that the Outer islands of Mauritius includes the islands of Mauritius, Rodrigues, Agaléga, Cargados Carajos and the Chagos Archipelago, including Diego Garcia and any other island comprised in the State of Mauritius. The Government of the Republic of Mauritius has stated that it does not recognise the British Indian Ocean Territory (BIOT) which the United Kingdom created by excising the Chagos Archipelago from the territory of Mauritius prior to its independence, and claims that the Chagos Archipelago including Diego Garcia forms an integral part of the territory of Mauritius under both Mauritian law and international law.
In 1965, the United Kingdom split the Chagos Archipelago away from Mauritius with the agreement of the Mauritian government, and the islands of Aldabra, Farquhar, and Desroches from the Seychelles, to form the British Indian Ocean Territory. The islands were formally established as an overseas territory of the United Kingdom on 8 November 1965. However, with effect from 23 June 1976, Aldabra, Farquhar, and Desroches were returned to the Seychelles on their attaining independence.
In 2012, the African Union and the Non-Aligned Movement have expressed unanimous support for Mauritius. On 18 March 2015, the Permanent Court of Arbitration unanimously held that the marine protected area (MPA) which the United Kingdom declared around the Chagos Archipelago in April 2010 was created in violation of international law. The Prime Minister of Mauritius has stated that this is the first time that the country's conduct with regard to the Chagos Archipelago has been considered and condemned by any international court or tribunal. He described the ruling as an important milestone in the relentless struggle, at the political, diplomatic, and other levels, of successive Governments over the years for the effective exercise by Mauritius of the sovereignty it claims over the Chagos Archipelago. The tribunal considered in detail the undertakings given by the United Kingdom to the Mauritian Ministers at the Lancaster House talks in September 1965. The UK had argued that those undertakings were not binding and had no status in international law. The Tribunal firmly rejected that argument, holding that those undertakings became a binding international agreement upon the independence of Mauritius, and have bound the UK ever since. It found that the UK's commitments towards Mauritius in relation to fishing rights and oil and mineral rights in the Chagos Archipelago are legally binding.
Beginning in the late 15th century, Portuguese explorers began to venture into the Indian Ocean and recorded the location of Mauritius and the other Mascarene Islands, Rodrigues and Réunion (the latter presently a French overseas department). In the 16th century, the Portuguese were joined by Dutch and English sailors, both nations having established East India Companies to exploit the commercial opportunities of the Indian Ocean and the Far East. Although Mauritius was used as a stopping point in the long voyages to and from the Indian Ocean, no attempt was made to establish a permanent settlement.
The first permanent colony in Mauritius was established by the Dutch East India Company in 1638. The Dutch maintained a small presence on Mauritius, with a brief interruption, until 1710 at which point the Dutch East India Company abandoned the island. Following the Dutch departure, the French government took possession of Mauritius in 1715, renaming it the Île de France.
The Chagos Archipelago was known during this period, appearing on Portuguese charts as early as 1538, but remained largely untouched. France progressively claimed and surveyed the Archipelago in the mid-18th century and granted concessions for the establishment of coconut plantations, leading to permanent settlement. Throughout this period, France administered the Chagos Archipelago as a dependency of the Ile de France.
In 1810, the British captured the Ile de France and renamed it Mauritius. By the Treaty of Paris of 30 May 1814, France ceded the Ile de France and all its dependencies (including the Chagos Archipelago) to the United Kingdom.
From the date of the cession by France until 8 November 1965, when the Chagos Archipelago was detached from the colony of Mauritius, the Archipelago was administered by the United Kingdom as a Dependency of Mauritius. During this period, the economy of the Chagos Archipelago was primarily driven by the coconut plantations and the export of copra (dried coconut flesh) for the production of oil, although other activities developed as the population of the Archipelago expanded. British administration over the Chagos Archipelago was exercised by various means, including by visits to the Chagos Archipelago made by Special Commissioners and Magistrates from Mauritius.
Although the broad outlines of British Administration of the colony during this period are not in dispute, the Parties disagree as to the extent of economic activity in the Chagos Archipelago and its significance for Mauritius, and on the significance of the Archipelago's status as a dependency. Mauritius contends that there were "close economic, cultural and social links between Mauritius and the Chagos Archipelago" and that "the administration of the Chagos Archipelago as a constituent part of Mauritius continued without interruption throughout that period of British rule". The United Kingdom, in contrast, submits that the Chagos Archipelago was only "very loosely administered from Mauritius" and "in law and in fact quite distinct from the Island of Mauritius." The United Kingdom further contends that "the islands had no economic relevance to Mauritius, other than as a supplier of coconut oil" and that, in any event, economic, social and cultural ties between the Chagos Archipelago and Mauritius during this period are irrelevant to the Archipelago's legal status.
Beginning in 1831, the administration of the British Governor of Mauritius was supplemented by the introduction of a Council of Government, originally composed of ex-officio members and members nominated by the Governor. The composition of this council was subsequently democratized through the progressive introduction of elected members. In 1947, the adoption of a new Constitution for Mauritius replaced the Council of Government with separate Legislative and Executive Councils. The Legislative Council was composed of the Governor as president, 19 elected members, 12 members nominated by the Governor and 3 ex-officio members.
The first election of the Legislative Council took place in 1948, and the Mauritius Labour Party (the "MLP") secured 12 of the 19 seats available for elected members. The MLP strengthened its position in the 1953 election by securing 14 of the available seats, although the MLP lacked an overall majority in the Legislative Council because of the presence of a number of members appointed by the Governor.
The 1953 election marked the beginning of Mauritius’ move towards independence. Following that election, Mauritian representatives began to press the British Government for universal suffrage, a ministerial system of government and greater elected representation in the Legislative Council. By 1959, the MLP-led government had openly adopted the goal of complete independence.
Constitutional Conferences were held in 1955, 1958, 1961, and 1965, resulting in a new constitution in 1958 and the creation of the post of Chief Minister in 1961 (renamed as the Premier after 1963). In 1962 Seewoosagur Ramgoolam became the Chief Minister within a Council of Ministers chaired by the Governor and, following the 1963 election, formed an all-party coalition government to pursue negotiations with the British on independence.
The final Constitutional Conference was held in London in September 1965 and was principally concerned with the debate between those Mauritian political leaders favouring independence and those preferring some form of continued association with the United Kingdom. On 24 September 1965, the responsible UK government minister, Anthony Greenwood, announced that the UK intended for Mauritius to become independent. Mauritius became independent on 12 March 1968. Section 111 of the Constitution of Mauritius states that "Mauritius" includes –
(a) the Islands of Mauritius, Rodrigues, Agaléga, Tromelin, Cargados Carajos and the Chagos Archipelago, including Diego Garcia and any other island comprised in the State of Mauritius; (b) the territorial sea and the air space above the territorial sea and the islands specified in paragraph (a); (c) the continental shelf; and (d) such places or areas as may be designated by regulations made by the Prime Minister, rights over which are or may become exercisable by Mauritius.
During negotiations on granting Mauritian independence, the UK proposed to separate the Chagos Archipelago from the colony of Mauritius, with the UK retaining the Chagos under British control. According to Mauritius, the proposal stemmed from a UK decision in the early 1960s to "accommodate the United States’ desire to use certain islands in the Indian Ocean for defence purposes."
The record before the Permanent Court of Arbitration sets out a series of bilateral talks between the United Kingdom and the United States in 1964 at which the two States decided that, in order to execute the plans for a military facility in the Chagos Archipelago, the United Kingdom would "provide the land, and security of tenure, by detaching islands and placing them under direct U.K. administration."
The suitability of Diego Garcia as the site of the planned military base was determined following a joint survey of the Chagos Archipelago and certain islands of the Seychelles in 1964. Following the survey, the United States sent its proposals to the United Kingdom, identifying Diego Garcia as its first preference as the site for the military facility. The United Kingdom and the United States conducted further negotiations between 1964 and 1965 regarding the desirability of "detachment of the entire Chagos Archipelago," as well as the islands of Aldabra, Farquhar and Desroches (then part of the Colony of the Seychelles). They further discussed the terms of compensation that would be required "to secure the acceptance of the proposals by the local Governments."
On 19 July 1965, the Governor of Mauritius was instructed to communicate the proposal to detach the Chagos Archipelago to the Mauritius Council of Ministers and to report back on the council's reaction. The initial reaction of the Mauritian Ministers, conveyed by the Governor's report of 23 July 1965, was a request for more time to consider the proposal. The report also noted that Sir Seewoosagur Ramgoolam expressed "dislike of detachment". At the next meeting of the council on 30 July 1965, the Mauritian Ministers indicated that detachment would be "unacceptable to public opinion in Mauritius" and proposed the alternative of a long-term lease, coupled with safeguards for mineral rights and a preference for Mauritius if fishing or agricultural rights were ever granted. The Parties differ in their understanding of the strength of, and motivation for, the Mauritian reaction. In any event, on 13 August 1965, the Governor of Mauritius informed the Mauritian Ministers that the United States objected to the proposal of a lease.
Discussions over the detachment of the Chagos Archipelago continued in a series of meetings between certain Mauritian political leaders, including Sir Seewoosagur Ramgoolam, and the Secretary of State for the Colonies, Anthony Greenwood, coinciding with the Constitutional Conference of September 1965 in London. Over the course of three meetings, the Mauritian leaders pressed the United Kingdom with respect to the compensation offered for Mauritian agreement to the detachment of the Archipelago, noting the involvement of the United States in the establishment of the defence facility and Mauritius’ need for continuing economic support (for example through a higher quota for Mauritius sugar imports into the United States), rather than the lump sum compensation being proposed by the United Kingdom. The United Kingdom took the firm position that obtaining concessions from the United States was not feasible; the United Kingdom did, however, increase the level of lump sum compensation on offer from £1 million to £3 million and introduced the prospect of a commitment that the Archipelago would be returned to Mauritius when no longer needed for defence purposes. The Mauritian leaders also met with the Economic Minister at the U.S. Embassy in London on the question of sugar quotas, and Sir Seewoosagur Ramgoolam met privately with Prime Minister Harold Wilson on the morning of 23 September 1965. The United Kingdom's record of this conversation records Prime Minister Wilson having told Sir Seewoosagur Ramgoolam that
The meetings culminated in the afternoon of 23 September 1965 (the "Lancaster House Meeting") in a provisional agreement on the part of Sir Seewoosagur Ramgoolam and his colleagues to agree in principle to the detachment of the Archipelago in exchange for the Secretary of State recommending certain actions by the United Kingdom to the Cabinet. The draft record of the Lancaster House Meeting set out the following:
Thereafter, Sir Seewoosagur Ramgoolam addressed a handwritten note to the Under-Secretary of State at the Colonial Office, Mr Trafford Smith, setting out further conditions relating to navigational and meteorological facilities on the Archipelago, fishing rights, emergency landing facilities, and the benefit of mineral or oil discoveries.
On 6 October 1965, instructions were sent to the Governor of Mauritius to secure "early confirmation that the Mauritius Government is willing to agree that Britain should now take the necessary legal steps to detach the Chagos Archipelago from Mauritius on the conditions enumerated in (i)–(viii) in paragraph 22 of the enclosed record [of the Lancaster House Meeting]." The Secretary of State went on to note that -
On 5 November 1965, the Governor of Mauritius informed the Colonial Office as follows:
The Governor also noted that "Parti Mauricien Social Démocrate (PMSD) Ministers dissented and (are now) considering their position in the government." The Parties differ regarding the extent to which Mauritian consent to the detachment was given voluntarily.
The detachment of the Chagos Archipelago was effected by the establishment of the British Indian Ocean Territory (BIOT) on 8 November 1965 by Order in Council. Pursuant to the Order in Council, the governance of the newly created BIOT was made the responsibility of the office of the BIOT Commissioner, appointed by the Queen upon the advice of the United Kingdom FCO. The BIOT Commissioner is assisted in the day-to-day management of the territory by a BIOT Administrator.
On the same day, the Secretary of State cabled the Governor of Mauritius as follows:
On 12 November 1965, the Governor of Mauritius cabled the Colonial Office, querying whether the Mauritian Ministers could make public reference to the items in paragraph 22 of the record of the Lancaster House Meeting and adding "[i]n this connection I trust further consideration promised . . . will enable categorical assurances to be given."
On 19 November 1965, the Colonial Office cabled the Governor of Mauritius as follows: U.K./U.S. defence interests;
A few weeks after the proposal to detach the islands from Mauritius, the United Nations General Assembly passed Resolution 2066(XX) on 16 December 1965, which stated that detaching part of a colonial territory was against customary international law and the UN Resolution 1514 passed on 14 December 1960. This resolution stated that "Any attempt aimed at the partial or total disruption of the national unity and the territorial integrity of a country is incompatible with the purposes and principles of the Charter of the United Nations."
After initially denying that the islands were inhabited, British officials forcibly expelled approximately 2,000 Chagossians to mainland Mauritius to allow the United States to establish a military base on Diego Garcia. Since 1971, the atoll of Diego Garcia is inhabited by some 3,000 UK and US military and civilian contracted personnel. The British and American governments routinely deny Chagossian requests for the right of return.
A marine protected area (MPA) around the Chagos Islands known as the Chagos Marine Protected Area was created by the British Government on 1 April 2010 and enforced on 1 November 2010. It is the world's largest official reserve, twice the size of Great Britain. The designation proved controversial as the decision was announced during a period when the UK Parliament was in recess. Despite the official designation as a marine reserve, the US military is fully exempt from fishing restrictions and the military base has been a major source of pollution to the area.
A leaked diplomatic cable dating back to 2009 reveal the British and US role in creating the marine nature reserve. The cable relays exchanges between US Political Counselor Richard Mills and British Director of the Foreign and Commonwealth Office Colin Roberts, in which Roberts "asserted that establishing a marine park would, in effect, put paid to resettlement claims of the archipelago’s former residents." Richard Mills concludes:
In March 2014, it was reported that the UK government would send experts to the islands to examine "options and risks" of resettlement.
The Government of Mauritius initiated proceedings on 20 December 2010 against the UK Government under the United Nations Convention on the Law of the Sea (UNCLOS) to challenge the legality of the ‘marine protected area’. Mauritius argues that Britain breached a UN resolution when it separated Chagos from the rest of the colony of Mauritius in the 1960s, before the country became independent, and that Britain therefore doesn't have the right to declare the area a marine reserve and that the MPA was not compatible with the rights of the Chagossians. The dispute was arbitrated by the Permanent Court of Arbitration. The sovereignty of Mauritius was explicitly recognized by two of the arbitrators and denied by none of the other three. Three members of the Tribunal found that they did not have jurisdiction to rule on that question; they expressed no view as to which of the two States has sovereignty over the Chagos Archipelago. Tribunal Judges Rüdiger Wolfrum and James Kateka held that the Tribunal did have jurisdiction to decide this question, and concluded that UK does not have sovereignty over the Chagos Archipelago. They found that:
On 18 March 2015, the Permanent Court of Arbitration ruled that the Chagos Marine Protected Area was illegal. The Tribunal's decision determined that the UK's undertaking to return the Chagos Archipelago to Mauritius gives Mauritius an interest in significant decisions that bear upon possible future uses of the archipelago. The result of the Tribunal's decision is that it is now open to the Parties to enter into the negotiations that the Tribunal would have expected prior to the proclamation of the MPA, with a view to achieving a mutually satisfactory arrangement for protecting the marine environment, to the extent necessary under a "sovereignty umbrella".
In 2004, following the decision of the British government to promulgate the British Indian Ocean Territory Order, which prohibited the Chagossians from remaining on the islands without express authorisation, Mauritius contemplated recourse to the International Court of Justice to finally and conclusively settle the dispute. However, article 36 of the International Court of Justice Statute provides that it is the option of the state whether it wishes to subject itself to the court's jurisdiction. Where the state chooses to be so bound, it may also restrict or limit the jurisdiction of the court in a number of ways. The UK's clause deposited at the court excluded, amongst other things, the jurisdiction of the court with regard "to any disputes with the government of any country which is a member of the Commonwealth with regard to situations or facts existing before 1 January 1969". The temporal limitation of 1 January 1969 was inserted to exclude all disputes arising during decolonisation. The effect of the British exclusionary clause would thus have prevented Mauritius from resorting to the court on the Chagos dispute because it is a member of the Commonwealth. When Mauritius threatened to leave the Commonwealth, the United Kingdom quickly amended its exclusion clause to exclude any disputes between itself, Commonwealth States and former Commonwealth States, thereby quashing any Mauritian hopes to ever have recourse to the contentious jurisdiction of the court, even if it left.
On 23 June 2017, the United Nations General Assembly (UNGA) voted in favour of referring the territorial dispute between Mauritius and the UK to the International Court of Justice (ICJ) in order to clarify the legal status of the Chagos Islands archipelago in the Indian Ocean. The motion was approved by a majority vote with 94 voting for and 15 against. In September 2018, the International Court of Justice began hearings on the case. Seventeen countries have argued in favour of Mauritius. The UK apologised for the "shameful" way islanders were evicted from the Chagos Archipelago but were insistent that Mauritius was wrong to bring the dispute over sovereignty of the strategic atoll group to the United Nations' highest court. The UK and its allies argued that this matter should not be decided by the court but should be resolved through bilateral negotiations, while bilateral discussions with Mauritius have been unfruitful over the past 50 years.
On 25 February 2019, the judges of the International Court of Justice by thirteen votes to one stated that the United Kingdom is under an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible. Only the American judge, Joan Donoghue, voted in favor of the UK. The president of the court, Abdulqawi Ahmed Yusuf, said the detachment of the Chagos Archipelago in 1965 from Mauritius had not been based on a "free and genuine expression of the people concerned". "This continued administration constitutes a wrongful act", he said, adding "The UK has an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible and that all member states must co-operate with the United Nations to complete the decolonization of Mauritius." Largely because of the detachment of the islands, the ICJ determined that the decolonization of Mauritius was still not lawfully completed. On 1 May 2019, the UK Foreign Office minister Alan Duncan stated that Mauritius has never held sovereignty over the archipelago and the UK does not recognise its claim. He stated that the ruling was merely an advisory opinion and not a legally binding judgment. Jeremy Corbyn, leader of the UK's main opposition party, wrote to the UK PM condemning her decision to defy a ruling of the UN's principal court that concluded that Britain should hand back the Chagos Islands to Mauritius. He expressed his concern that the UK government appears ready to disregard international law and ignore a ruling of the international court and the right of the Chagossians to return to their homes.
While the UN advisory opinion and resolutions are not legally binding, it carries significant political weight since the ruling came from the UN's highest court and the assembly vote reflects world opinion. The ruling of the ICJ would be similar if the UK agreed to go for a contentious case. The resolution also has immediate practical consequences: the UN, its specialised agencies, and all other international organisations are now bound, as a matter of UN law, to support the decolonisation of Mauritius even if the UK continue to claim that it has no doubt about its sovereignty.
On 22 May 2019, the United Nations General Assembly debated and adopted a resolution that affirmed that the Chagos Archipelago, which has been occupied by the UK for more than 50 years, "forms an integral part of the territory of Mauritius". The resolution gives effect to an advisory opinion of the International Court of Justice (ICJ), demanded that the UK "withdraw its colonial administration ... unconditionally within a period of no more than six months". 116 states voted in favour of the resolution, 55 abstained and only Australia, Hungary, Israel and Maldives supported the UK and US. During the debate, the Mauritian Prime Minister described the expulsion of Chagossians as "a crime against humanity".
Following the International Court of Justice (ICJ) advisory opinion in 2019 and the subsequent United Nations General Assembly (UNGA) resolution, several international organizations updated their official maps to reflect Mauritius' sovereignty over the Chagos Archipelago. The United Nations (UN), in compliance with the UNGA resolution, amended its official map on 20 February 2020 with Map No. 4170 Revision 18.1, recognizing the Chagos Islands as part of Mauritius instead of British territory.
The Maldives is involved in a dispute with Mauritius regarding the boundaries of their respective Exclusive Economic Zones (EEZs), particularly in relation to the EEZ of the Chagos Archipelago. In June 2019, Mauritius initiated arbitral proceedings against the Maldives at the International Tribunal for the Law of the Sea (ITLOS) to resolve the maritime boundary between the Maldives and the Chagos Archipelago. Among its preliminary objections, the Maldives argued that a sovereignty dispute existed between Mauritius and the United Kingdom over the Chagos Archipelago, and that this issue fell outside ITLOS's jurisdiction. On 28 January 2021, ITLOS ruled that the sovereignty dispute between the United Kingdom and Mauritius had already been definitively addressed through the International Court of Justice’s (ICJ) earlier Advisory Opinion, which affirmed that the United Kingdom has no sovereignty over the Chagos Archipelago. Consequently, ITLOS declared there was no jurisdictional barrier, dismissing all five of the Maldives' preliminary objections and accepting Mauritius' claims as admissible.
The Universal Postal Union (UPU), a UN specialized agency for postal matters, officially recognized the Chagos Archipelago as part of Mauritius on 27 August 2021. The decision was made during the 27th Universal Postal Congress in Abidjan, Côte d'Ivoire, with 77 votes in favor, 6 against, and 41 abstentions. As a result, the UPU will no longer register, distribute, or forward postage stamps from the "British Indian Ocean Territory," which previously included the Chagos Archipelago. This follows the 2019 UN General Assembly directive, based on advice from the International Court of Justice, affirming Mauritius' sovereignty over the archipelago. The UPU, as a UN agency, is required to align with UN decisions, bringing the matter to its governing body for resolution. All post from the Chagos Islands must now bear stamps from Mauritius and stamps marked British Indian Ocean Territory now won't be recognised.
Section 76B of the Criminal Code in Mauritius was introduced through the Criminal Code (Amendment) Act 2021, which was amended on 26 November 2021. This provision aims to protect Mauritius’ territorial integrity by criminalizing actions that misrepresent its sovereignty over any part of its territory.
The law applies to individuals acting under the authority, instructions, or financial support (direct or indirect) of a foreign state. Offenses include:
Definition of a Foreign State
A "foreign state" under this provision refers to any country that an international court or tribunal has determined to have no valid claim over any part of Mauritius' territory.
Persons found guilty of violating this law may face:
The law applies extraterritorially, meaning that offenses committed outside Mauritius are still considered as having been committed within the country. The Intermediate Court has jurisdiction over such cases and can impose the prescribed penalties.
In May 2022, the Food and Agriculture Organization issued a legal opinion asserting that the United Kingdom should no longer be recognized as a "coastal state" in the Indian Ocean, due to the disputed status of the Chagos Archipelago. This position follows UN General Assembly resolution 73/295, which affirms the Chagos Archipelago as part of Mauritius. Consequently, the UK is now considered a state that fishes in the region but does not hold the rights or obligations of a coastal state under the Indian Ocean Tuna Commission framework.
On 3 November 2022, the Secretary of State for Foreign, Commonwealth and Development Affairs, James Cleverly, stated that the United Kingdom and Mauritius had committed to negotiating an agreement based on international law to resolve outstanding issues, including those concerning the former inhabitants of the Chagos Archipelago. This agreement aims to strengthen bilateral cooperation on regional and global security challenges, particularly in the Indian Ocean. Key areas of focus include maritime security, environmental conservation, climate change, human rights, and efforts to combat illegal migration, fishing, drug, and arms trafficking. Cleverly also reaffirmed that any agreement would ensure the continued effective operation of the joint UK-US military base on Diego Garcia, recognizing its strategic importance. The negotiations will also consider the interests of key regional partners, including the United States and India. The UK and Mauritius have agreed to engage in constructive discussions with the goal of reaching an agreement by early next year.
On 3 October 2024, the UK and Mauritius issued a joint statement, affirming Mauritius' sovereignty over the Chagos Archipelago while granting the UK continued control over Diego Garcia for 99 years. This agreement implicitly indicates that the UK will maintain sovereignty over Diego Garcia, which hosts a critical military base. Additionally, provisions for Chagossians, regional security, and environmental cooperation are included, strengthening bilateral ties between the two nations.
In his October 2024 statement on the Chagos Islands, Foreign Secretary David Lammy discussed the contested status of the territory and the UK-US military base. He emphasized the unsustainability of the status quo and the inevitability of a binding judgment against the UK. Lammy acknowledged the only viable path was negotiating a deal to ensure the base's continued operation and international law compliance, avoiding the choice of abandoning the base or breaking international law.
After the general elections in Mauritius, Navin Ramgoolam became the Prime Minister on 13 November 2024. Upon assuming office, Ramgoolam received a letter from British Prime Minister Keir Starmer on 12 November 2024, informing him of plans to send British political envoy Jonathan Powell to Mauritius. On 25 November 2024, Powell arrived in Mauritius and briefed the Prime Minister on the current status of the agreement. During the meeting, the Prime Minister expressed surprise that the agreement had been made shortly before the dissolution of Parliament, with the opposition being unaware of the negotiations.
On 20 December 2024, the UK and Mauritius issued a joint statement outlining their commitment to resolving the sovereignty dispute over the Chagos Archipelago. The agreement will transfer sovereignty to Mauritius while preserving the operations of the Diego Garcia military base. Both nations have pledged to complete the treaty process promptly.
Following Powell’s visit, the Prime Minister ordered an independent review of the confidential draft agreement. The document, which had been presented to the new Mauritian government after the 2024 general elections, was unknown to the officials before the change in leadership. This review was conducted by an inter-ministerial committee comprising the Deputy Prime Minister, Attorney General, and Minister of Foreign Affairs, Regional Integration, and International Trade.
A senior delegation from the United Kingdom visited Mauritius from 9–12 December 2024 to engage in further discussions. While meetings were held between the senior officials of both countries, the UK delegation also met with the Prime Minister to discuss the specifics of the draft agreement. Mauritius expressed its willingness to conclude an agreement but made it clear that the draft presented did not meet the nation’s expectations. The government proposed counterproposals to the United Kingdom, seeking to negotiate terms that were more favourable to Mauritius.
On 16 December 2024, the United Kingdom responded to Mauritius' counterproposals. These responses were considered by the inter-ministerial committee, which led to a further exchange of proposals. On 31 December 2024, Mauritius submitted its final response and suggested a meeting in London to finalize the agreement.
On 13 January 2025, the governments of the UK and Mauritius issued a joint statement regarding the Chagos Archipelago. They affirmed progress in their discussions, working towards a treaty that would establish Mauritius as the sovereign authority over the archipelago while ensuring the continued operation of the Diego Garcia base. The talks are ongoing, aiming to reach a mutually beneficial agreement.
On 15 January 2025, a special Cabinet meeting was convened to discuss the progress of the negotiations. However, before the meeting, Mauritius was informed by the UK that, in light of the imminent change in the United States administration, they would await the views of the new US administration before finalizing the agreement. Despite this, a delegation from Mauritius, led by the Attorney General, travelled to the UK on 16–17 January 2025 to continue discussions. During these meetings, UK officials, including Lord Hermer and Under Secretary of State Stephen Doughty, reassured the Mauritian delegation of the UK's commitment to signing the agreement. The Mauritian government expressed strong concerns about the draft agreement proposed by the UK, citing several key issues that needed to be addressed:
The Mauritian government rejected the draft, arguing that it was a “sell-out” and that the terms would not benefit the nation in the long term. The Prime Minister insisted that the agreement needed to be renegotiated to secure better terms for Mauritius. The British Prime Minister, in a telephone conversation with the Prime Minister of Mauritius on 2 February 2025, indicated that the UK government intended to proceed with the agreement on the Chagos Archipelago. While the agreement had reached a near-final stage, the UK’s decision to wait for the new US administration’s views delayed the signing. However, the Mauritian government remained confident that a resolution would be reached shortly, with the Prime Minister stating that negotiations would continue with the aim of securing a mutually beneficial agreement.
On 5 February 2025, Stephen Doughty, the Minister of State for Europe, North America and Overseas Territories, emphasized that international legal rulings have cast doubt on Britain's sovereignty over the Chagos Islands, making a deal with Mauritius crucial to ensuring the continued operation of the US military base on Diego Garcia. He highlighted the UK's control over the electromagnetic spectrum used for satellite communications, governed by the International Telecommunication Union, noting that while Britain could still communicate without it, others could also use the spectrum, threatening the base's security. Doughty further outlined the UK's full control over Diego Garcia, including a buffer zone and mechanisms to prevent interference, underscoring that a future deal with Mauritius would secure the base's operations and national security, free from external risks.
On 27 February 2025, speaking in the Oval Office alongside Prime Minister Keir Starmer, U.S. President Donald Trump stated that he was willing to support the agreement to transfer sovereignty of the Chagos Islands to Mauritius. Ramgoolam described Trump's comments as seeming positive, but said the Mauritian government would still need to wait to see Britain's final proposals. The Daily Telegraph reported on 2 March 2025 that according to a senior source, Trump's public statements were taken as the approval the British government had been waiting for to continue making progress, and that the UK and Mauritius were expected to finalise the deal as early as 4 March, although the formal endorsement of the U.S. would be required before it could be finalised and signed.