In 1965, the United Kingdom split its administration of the Chagos Archipelago away from Mauritius and into theBritish Indian Ocean Territory (BIOT). The islands were formally established as an overseas territory of the United Kingdom on 8 November 1965.[5]
The British government separated the Chagos Archipelago from Mauritius, creating a new colony, the British Indian Ocean Territory (BIOT). To avoid accountability to the United Nations for its continued colonial rule, the UK falsely claimed that the Chagos had no permanent population.[6]
The Chagos Islands had been home to theChagossians, aBourbonnais Creole–speaking people, until the United Kingdomexpelled them from the archipelago at the request of theUnited States between 1967 and 1973 to allow the United States to buildNaval Support Facility Diego Garcia, which operates under a special agreement allowing significant US military presence. The main forcible removal of Diego Garcia's population took place in July and September 1971.[7] Since 1971 only the atoll of Diego Garcia has been inhabited, and only by employees of the military including civilian contracted personnel. Since being expelled, Chagossians have been prevented from entering the islands.
Mauritius was engaged in asovereignty dispute with the UK, claiming the Chagos Archipelago as part of Mauritius. TheInternational Court of Justice (ICJ) and theInternational Tribunal for the Law of the Sea both stated that the UK had an obligation to return the islands to Mauritius.[8][9][10] In October 2024, the British government announced it would transfer the Chagos Islands to Mauritius subject to finalisation of a treaty.[11] The transfer agreement was signed on 22 May 2025, with the provision that the island of Diego Garcia would be leased back to the UK for at least 99 years.[12] The UK government expects the treaty to be ratified near the end of 2025.[13]
The land area of the islands is 56.1 km2 (21.7 sq mi), the largest island, Diego Garcia, having an area of 32.5 km2 (12.5 sq mi). The total area, including lagoons within atolls, is more than 15,000 km2 (5,800 sq mi), of which 12,642 km2 (4,881 sq mi) are accounted by theGreat Chagos Bank, the largest acknowledged atoll structure of the world (the completely submergedSaya de Malha Bank is larger, but its status as an atoll is uncertain). Theshelf area is 20,607 km2 (7,956 sq mi), and theExclusive Economic Zone, which borders the corresponding zone of the Maldives in the north, has an area of 639 km2 (247 sq mi) (includingterritorial waters).
The Chagos group is a combination of differentcoralline rock structures topping asubmarine ridge running southwards across the centre of the Indian Ocean, formed by volcanoes above theRéunion hotspot. Unlike the Maldives, there is no clearly discernible pattern in the atoll arrangement, which makes the whole archipelago look somewhat chaotic. Most of the coralline structures of the Chagos are submerged reefs.
The Chagos contain the world's largest coral atoll, The Great Chagos Bank, which supports half the total area of good quality reefs in the Indian Ocean. As a result, the ecosystems of the Chagos have so far proven resilient toclimate change and environmental disruptions.
The largest individual islands are Diego Garcia (32.5 km2 or 12.5 sq mi), Eagle (Great Chagos Bank, 3.1 km2 or 1.2 sq mi),Île Pierre (Peros Banhos, 1.4 km2 or 0.54 sq mi), Eastern Egmont (Egmont Islands, 2.175 km2 or 0.840 sq mi),Île du Coin (Peros Banhos, 1.32 km2 or 0.51 sq mi) andÎle Boddam (Salomon Islands, 1.27 km2 or 0.49 sq mi).
In addition to the seven atolls with dry land reaching at least the high-water mark, there are nine reefs andbanks, most of which can be considered permanently submerged atoll structures. The number of atolls in the Chagos Archipelago is given as four or five in most sources, plus two island groups and two single islands, mainly because it is not recognised that the Great Chagos Bank is a huge atoll structure (including those two island groups and two single islands), and becauseBlenheim Reef, which has islets or cays above or just reaching the high-water mark, is not included. Features are listed in the table from north to south:
Map this section's coordinates usingOpenStreetMapDownload coordinates asKML
Salomon Atoll is one of the many above water features of the Chagos Archipelago.The Chagos Archipelago is a hotspot ofbiodiversity in the Indian Ocean.
The mainnatural resources of the area arecoconuts and fish. The licensing ofcommercial fishing used to provide an annual income of aboutUS$2million[as of?] for the British Indian Ocean Territory authorities. However, licenses have not been given since October 2010; the last expired after the creation of the no-take marine reserve.[14]
All economic activity is concentrated on the largest island of Diego Garcia, where joint UK–US military facilities are located. Construction projects and various services needed to support the military installations are done by military and contract employees from the UK, Mauritius, thePhilippines, and the US. There are currently no industrial or agricultural activities on the islands. All the water, food and other essentials of daily life are shipped to the island. An independent feasibility study led to the conclusion that resettlement would be "costly and precarious".[This quote needs a citation] Another feasibility study, commissioned by organisations supporting resettlement, found that resettlement would be possible at a cost to the British taxpayer of£25million.[as of?][citation needed] If the Chagossians return, they plan to re-establishcopra production and fishing, and to begin the commercial development of the islands for tourism.
Until October 2010,Skipjack (Euthynnus pelamis) andyellowfin tuna (Thunnus albacares) were fished for about two months of the year as their year-long migratory route takes them through Chagos waters. While the remoteness of the Chagos offers some protection from extractive activities, legal and illegal fishing have had an impact. There is considerablepoaching of turtles and other marine life. Sharks, which play a vital role in balancing the food web of tropical reefs, have suffered sharp declines fromillegal fishing for their fins and asbycatch in legal fisheries.Sea cucumbers, which cleanse sand, are poached to feed Asian markets.
The Chagos Archipelago has atropicaloceanic climate; hot andhumid but moderated bytrade winds.Climate is characterised by plenty of sunshine, warm temperatures, showers and light breezes.December through February is considered the rainy season (summer monsoon); typical weather conditions include light west-northwesterly winds and warmer temperatures with more rainfall. June to September is considered the drier season (winter), characterised by moderate south-easterly winds, slightly cooler temperatures and lessrainfall. The annual mean rainfall is 2,600 millimetres (100 in), varying from 105 millimetres (4.1 in) during August to 350 millimetres (14 in) during January.
According to SouthernMaldivianoral tradition, local traders and fishermen were occasionally lost at sea and became stranded in one of the islands of the Chagos. Eventually they were rescued and brought back home.[15] However, these islands were judged to be too far away from the Maldives to be settled permanently byMaldivians. Thus, for many centuries, the Chagos were ignored by their northern neighbours. However, these tales contrast with the historical view that the Maldives has towards the Chagos, as they were considered to be an extension of Maldivian maritime territory. For centuries, the Maldivians have used the Chagos as a base for fishing expeditions. People would camp on the islands, catch fish, and cook, smoke, and dry them.[citation needed] Additionally, the exiled Maldive King Hassan IX (also known as Dom Manoel), while inCochin, describes himself in his letters patent of 1561 as King of the Maldive islands, including seven of the islands of Pullobay, referring toFōlhavahi or the Chagos, and this letter survives in a Portuguese archive in Lisbon.[16][17]
In Maldivian lore the whole group is known asFōlhavahi orHollhavai (Dhivehi:ފޯޅަވަހި or ހޮއްޅަވައި) (the latter name in the Southern MaldivesAdduan dialect ofDhivehi). There are no separate names for the different atolls of the Chagos in the Maldivian oral tradition;Fayhandheeb is used for the Archipelago as a whole. According to Maldivian history, the Maldives Archipelago consists of Mahaldheeb, Suvaadheebu and Feyhandheeb.[18]
Nautical chart of the Chagos Archipelago from Moresby's survey of 1837
The first Europeans to become aware of the archipelago werePortuguese explorers. Although the Portuguese navigatorPedro de Mascarenhas (1470 – 23 June 1555) is credited with having encountered the islands during his voyage of 1512–13, there is little corroborative evidence; cartographic analysis points to 1532 or later.[citation needed]Portuguese seafarers named the groupBassas de Chagas,[19]Chagas (lit.'wounds') referring to theHoly Wounds of thecrucifixion of Jesus. They also named some of the atolls, such as Diego Garcia andPeros Banhos Atoll, mentioned asPedro dos Banhos in 1513 byAfonso de Albuquerque.[20] This lonely and isolated group, economically and politically uninteresting to the Portuguese, was never made part of thePortuguese Empire.[21]
The earliest and most interesting description of the Chagos, before coconut trees grew widely on the islands, was written by Manoel Rangel, a castaway from the Portuguese shipConceição which ran aground on the Peros Banhos reefs in 1556.[22]
The oldest known written document claiming the Chagos is attributed to King Hassan IX of the Maldives in the year 1561.[17] TheFrench were the first European colonial power to lay claim to the Chagos after they settledÎle Bourbon (nowRéunion, in 1665) andIsle de France (now Mauritius, in 1715). The French began issuing permits for companies to establish coconut oil plantations on the Chagos in the 1770s.[23]
On 27 April 1786 the Chagos Islands and Diego Garcia were claimed forGreat Britain. However, the territory was ceded toBritain by treaty only afterNapoleon's defeat, in 1815. The Chagos were governed from Mauritius, which was by that time also a British colony.[24]
In 1793, when the first successful colony was founded on Diego Garcia, the largest island,coconutplantations were established on many of the atolls and isolated islands of the archipelago. The workers were enslaved by the British and not freed until 1840, after which time many of the workers descended from those who had earlier been enslaved. They formed an inter-island culture calledIlois, aFrench Creole word meaning'islanders'.
CommanderRobert Moresby made a survey of the Chagos on behalf of theBritish Admiralty in 1837–1838. After Moresby had taken measurements of most of the atolls and reefs, the archipelago was charted with relative precision for the first time.[25]
Moresby's survey
Robert Moresby was a captain of theEast India Company's Bombay Marine/Indian Navy who distinguished himself as a hydrographer, maritime surveyor and draughtsman.
After his completion of the Red Sea Survey, Moresby was sent to chart various coral island groups lying across the track of India-to-Cape trade. In 1834–36 Moresby, assisted by Lieutenants Christopher and Young, undertook the difficult cartography of the Maldive Islands, drawing the first accurate maritime charts of this complicated Indian Ocean atoll group (Admiralty Charts). These charts were printed as three separate large maps by the Hydrographic Service of the Royal Navy.
Moresby's survey of the Atolls of the Maldives was followed by the Chagos Archipelago. where he conducted "a thorough scientific survey".[This quote needs a citation] He planted 30breadfruit trees in Diego Garcia Island, the largest of the group. Moresby reported that "there were cats and chickens on the island".[citation needed]
On 31 August 1903 the Chagos Archipelago was administratively separated from theSeychelles and attached to Mauritius.[26]
Before granting independence to Mauritius, the United Kingdom paid£3million[when?] in compensation to the Mauritius Government and made several undertakings regarding the future status of the Chagos Archipelago. These included a commitment that the archipelago would be returned to Mauritius if it was no longer needed for defence purposes, assurances that Mauritius would retain access to navigational and meteorological facilities as well as fishing rights, and an agreement that any benefits from minerals or oil discovered in or near the Chagos Archipelago would revert to Mauritius. The compensation was intended to support development projects and address the resettlement of the displaced Chagossian community, though its adequacy and distribution have remained subjects of controversy.[27] Various press articles have wrongly suggested that the £3million payment was for the purchase of the islands from Mauritius, when in fact it was compensation tied to the detachment of the archipelago and broader commitments made by the British government.[28]
On 25 May 1967, less than two years after the agreement with Premier Seewoosagur Ramgoolam, Prime Minister Harold Wilson attended a Cabinet Committee meeting alongside the Chancellor of the Exchequer and the Secretaries of State for Commonwealth Affairs, Economic Affairs, Defence, and the Home Department. During this meeting, the Commonwealth Secretary noted that at the time of the 1965 agreement, Mauritian ministers were unaware of Britain's negotiations with the United States for a financial contribution toward the compensation. Mauritian officials were also informed that there would be no additional contribution from the United States, as this was a matter solely between the UK and Mauritius. The British government made it clear that the £3 million was the maximum it could afford and that if Mauritius did not accept the proposal, the UK would not proceed with arrangements for granting independence.[29]
During the same meeting, the Secretary of State for Defence stated that when the British Indian Ocean Territory was established, the UK had arranged compensation for both Mauritius and the Seychelles for the detachment of islands, with a total budget of approximately £10 million. The United States had agreed to contribute up to half of this amount, with a maximum of £5 million. To avoid potential embarrassment in the US Congress, the US government requested that its financial contribution remain secret. As a result, it was arranged that the US contribution would be concealed by waiving certain payments owed by the UK to the US in connection with the development of the Polaris missile program.[27][30]
On 30 December 1966, the United States and the United Kingdom executed an agreement through an Exchange of Notes which permit theUnited States Armed Forces to use any island of the BIOT for defence purposes for 50 years, until December 2016,[28] followed by a 20-year optional extension (to 2036) to which both parties must agree by December 2014. As of 2010[update], only the atoll of Diego Garcia has been transformed into a military facility.
In 1967 the British Government bought the entire assets and real property of theSeychellois Chagos Agalega Company,[31] which owned all the islands of the BIOT,[32] for £660,000,[33] equivalent to£13.1million in 2023, and administered them as a government enterprise while awaiting US funding of its proposed facilities, with an interim objective of paying for the administrative expenses of the new territory. The plantations, under their previous private ownership and under government administration, proved consistently unprofitable due to the introduction of new oils and lubricants in the international marketplace and the establishment of vast coconut plantations in theEast Indies and thePhilippines.
Between 1967 and 1973, the population was forcibly removed from the islands and moved to Mauritius and theSeychelles to make way for a joint United States–United Kingdom military base onDiego Garcia.[34] In March 1971,United States naval construction battalions (Seabees), arrived on Diego Garcia to begin the construction of the Communications Station and an airfield. To satisfy the terms of an agreement between the United Kingdom and the United States for an uninhabited island, the plantation on Diego Garcia was closed in October of that year.[35]
The plantation workers and their families were initially deported to the plantations onPeros Banhos andSalomon atolls in the group; those who requested were transported to the Seychelles or Mauritius. In 1972, the UK closed the remaining plantations (all being now uneconomic) of the Chagos, and deported the Ilois who would have faced economic hardship to the Seychelles or Mauritius. The independent Mauritian government refused to accept these further displaced islanders without payment and in 1973, the United Kingdom agreed and gave them an additional £650,000, equivalent to£8.4million in 2023, as reparation payments to resettle the people.[36] Some people were of the view that they were rehoused and employed under worse conditions than other Mauritians. The islands were becoming costly to live in due to industrial moves away from coconut oils and copra fibre markets and the success of larger plantations in the far east.
On 13 October 2009, the Cabinet of the Maldives Government decided to see if the Maldives can claim for an extended continental shelf.[38]
On 26 July 2010, the Republic of Maldives submitted to the Commission on the Limits of the Continental Shelf, in accordance with Article 76, paragraph 8, of theUnited Nations Convention on the Law of the Sea, information on the limits of thecontinental shelf beyond 200nautical miles (370 km; 230 mi) from the baselines from which the breadth of the territorial sea is measured.[39]
On 1 April 2010, the British government announced the establishment of theChagos Marine Protected Area as the world's largestmarine reserve. At 640,000 km2 (250,000 sq mi), it is larger than both France and the US state ofCalifornia. It doubled the total area of environmental no-take zones worldwide.[40] On 18 March 2015, thePermanent Court of Arbitration unanimously held that themarine protected area (MPA) which the United Kingdom declared around the Chagos Archipelago in April 2010 violates international law.Anerood Jugnauth,Prime Minister of Mauritius, pointed out that it is the first time that the United Kingdom's conduct with regard to the Chagos Archipelago has been considered and condemned by any international court or tribunal.[41][42]
On 20 December 2010 Mauritius initiated proceedings against the United Kingdom under theUnited Nations Convention on the Law of the Sea (UNCLOS) to challenge the legality of the Chagos Archipelago MPA.[43]
The issue of compensation and repatriation of the former inhabitants of several of the archipelago's atolls, exiled since 1973, continued in litigation, and in 2010 it was submitted to theEuropean Court of Human Rights by a group of former residents.[44]
Litigation continued in 2012 regarding the right of return for the displaced islanders and Mauritian sovereignty claims. In addition, advocacy on the Chagossians' behalf continues both in the United States and in Europe. In 2018, Mauritius took the matter to theInternational Court of Justice for an advisory opinion, against British objections.[45]
In 2014, a Feasibility Study for the Resettlement of the British Indian Ocean Territory was undertaken by the UK Government by consultants fromKPMG.
The objectives of the study were to assess costs and sustainability of resettlement over five, ten, and twenty years, evaluate economic self-sufficiency, risks, and environmental implications, explore potential resettlement options ranging from small-scale pilot projects to larger-scale resettlements.
A neutral analysis was undertaken, including consultations with the Chagossian community and environmental assessments.Options considered included modern lifestyles, subsistence living, eco-villages, and research stations.Legal, environmental, infrastructure, and economic aspects were analysed.
Large-scale resettlement (1,500 people), medium-scale (500 people), and a pilot scheme (150 people) were proposed. Diego Garcia was a preferred location due to existing infrastructure, withIle du Coin and Boddam also being provisional initial candidate sites.
Chagossians expressed a strong preference for permanent resettlement, not temporary visits.They emphasized the need for modern living standards, environmental conservation, and access to UK-level education and healthcare.
Most islands are low-lying and vulnerable to climate change, with varying suitability for habitation.Environmental protections and monitoring would be critical.
Employment opportunities could include tourism, fishing, and environmental monitoring.High-end and eco-tourism were seen as potential revenue generators.
Amendments to BIOT's legal framework would be required to facilitate resettlement. Governance models could draw from other small British Overseas Territories likePitcairn andAscension Island.[46][47][page needed]
In November 2016, the United Kingdom restated it would not permit Chagossians to return to the islands.[48]
In July 2021, theChagos Refugees Group UK submitted a complaint to the Irish government against domain-name speculatorsPaul Kane andEthos Capital subsidiaryAfilias, seeking repatriation of the.io (that is,Indian Ocean) country-code top-level domain and payment of back royalties from theUS$7million per year in revenue generated by the domain.[49] While attempts to repatriate top-level domains are not uncommon, this one is notable in that it cites consumer and human rights violations of theOECD's 2011Guidelines for Multinational Enterprises rather thanmultistakeholder representation underICANN policy, and because the .io domain has enjoyed commercial success, particularly amongcryptocurrency companies, with more than 270,000 domains registered.[50][51]
The Chagos had been administered from imperial offices in Mauritius since the 18th century when the French first named the islands. All of the islands forming part of the French colonial territory ofIsle de France (as Mauritius was often then known) were ceded to the British in 1810 under theAct of Capitulation. In 1965, in planning before Mauritian independence, the UK split the archipelago from the territory of Mauritius to form the British Indian Ocean Territory, looking to provide the United States, which was the country's main creditor following the turmoil of the Second World War, with an uninhabited island base,.[3]
The United Nations' resolutions on self-determination deprecated the parcelling up of imperial territories before independence, without its endorsement and local support, mindful of thePartition of India which provided the strong governments sought by the separate factions but failed to ensure a relatively peaceful transfer of power in many places. Mauritius has repeatedly stated that the British claim that the Chagos Archipelago is one of its territories thwarted its claim to what would be widely considered part of the Mauritian colony and also breached UN resolutions. The UK has stated that the Chagos will be assigned to Mauritius once the islands are no longer required for defence purposes.[3]
The island nation of Mauritius claims the Chagos Archipelago (which is coterminous with the BIOT), including Diego Garcia. Maldives states that the UK's claim to a 200-nautical-mile (370 km; 230 mi)Exclusive Economic Zone around the Chagos Archipelago is invalid as the islands are considered uninhabited.[clarification needed][52] A subsidiary issue is the Mauritian opposition to the 1 April 2010 UK Government's declaration that the BIOT is aMarine Protected Area with fishing and extractive industry (including oil and gas exploration) prohibited.[53]
On 16 November 2016, the UK Foreign Office maintained their ban onrepatriation of the islands.[48] In response to this decision, the Prime Minister of Mauritius expressed his country's plan to advance the sovereignty dispute to theInternational Court of Justice.[54] British Foreign SecretaryBoris Johnson sought Indian assistance for resolving the dispute involving the UK, the US, and Mauritius. India has maintained considerable influence in Mauritius through deep cultural and economic ties. India has maintained that the matter of whether or not to proceed with the UN General Assembly move is a decision for the Mauritian government to make.[55]
On 22 June 2017, theUnited Nations General Assembly (UNGA) requested theInternational Court of Justice (ICJ) to give an advisory opinion on the separation of the Chagos Archipelago from Mauritius. On 25 February 2019, the International Court of Justice advised that in its opinion:
"at the time of its detachment from Mauritius" the "Chagos Archipelago was clearly an integral part of that non-self-governing territory";[56]
the United Kingdom's purported detachment of the Chagos Archipelago "was not based on the free and genuine expression of the will of the people concerned";[56]
at the time of the purported detachment, "obligations arising under international law and reflected in the resolutions adopted by the General Assembly during the process of decolonization of Mauritius require[d] the United Kingdom, as the administering Power, to respect the territorial integrity of that country, including the Chagos Archipelago";[56]
the "detachment" was therefore "unlawful" such that "the process of decolonization of Mauritius was not lawfully completed when Mauritius acceded to independence in 1968"[56]
"the United Kingdom's continued administration of the Chagos Archipelago constitutes a wrongful act entailing the international responsibility of that State";[56]
this "unlawful act" is "of a continuing character" and "the United Kingdom is under an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible";[56] and
"all Member States [of the United Nations] are under an obligation to co-operate with the United Nations in order to complete the decolonization of Mauritius."[56]
On 23 June 2017, the UNGA voted in favour of referring the territorial dispute between Mauritius and the United Kingdom to the 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.[57][58]
On 22 May 2019, the United Nations General Assembly debated and adopted a resolution that affirmed that the Chagos archipelago "forms an integral part of the territory of Mauritius." The resolution 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 5 countries supported theUnited Kingdom. During the debate, the Mauritian Prime Minister,Sir Anerood Jugnauth, described the expulsion of Chagossians as "akin to acrime against humanity", while the United Kingdom continued to assert that it had no doubt about its sovereignty over the archipelago.[59] The Maldives were one of the countries which supported the UK in the General Assembly vote. It stated that, if the Chagos Archipelago became inhabited, the Maldives claim to an extension of itsExclusive Economic Zone would be affected. The resolution's immediate consequence was that the UN and other international organisations became bound by UN law to support the decolonisation of the Chagos Islands.
On 25 February 2019, the ICJ delivered an advisory opinion that placing the Archipelago under British administration in 1965 was not based upon the free expression of the inhabitants and that it thus advised that the United Kingdom should relinquish the archipelago, including the strategic United States military base, for the establishment of which approximately 1,500 inhabitants had been deported. TheBritish government rejected any jurisdiction of the court to deliberate these matters.[60]
China abstained in the 2019 UN vote, which was a step towards reaching an agreement to return the Chagos Archipelago to Mauritius.[61]
The UNGA voted in favour of setting a six-month deadline for the United Kingdom to withdraw from the Chagos Archipelago, which would then be reunified with Mauritius. The motion was approved by a majority vote with 116 voting for and 6 against. Fifty-six states, including France and Germany, abstained.[62][63]
On 28 January 2021, the United Nation'sInternational Tribunal for the Law of the Sea (ITLOS) confirmed the International Court of Justice ruling and ordered Britain to hand over the Chagos Archipelago to Mauritius.[64] The ITLOS Special Chamber affirmed that: "it is inconceivable that the United Kingdom, whose administration over the Chagos Archipelago constitutes a wrongful act of a continuing character and thus must be brought to an end as rapidly as possible, and yet who has failed to do so, can have any legal interests in permanently disposing of maritime zones around the Chagos Archipelago by delimitation".[65]
In August 2021, theUniversal Postal Union banned BIOT stamps from being used in the BIOT, a move Mauritian Prime MinisterPravind Jugnauth called a "big step in favour of the recognition of the sovereignty of Mauritius over the Chagos".[66][failed verification]
On November 26, 2021, Mauritius amended its Criminal Code through the Criminal Code (Amendment) Act 2021 to introduce Section 76B, which criminalizes actions that misrepresent Mauritius' 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 and imposes penalties of a fine or imprisonment of up to 10 years. Offenses include producing, distributing, or marketing coins, stamps, maps, or official documents that misrepresent Mauritius' sovereignty, as well as instructing others to do so. 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.[67]
On 14 February 2022, a delegation from Mauritius, including the Mauritian ambassador to the UN, raised the Mauritian flag on the Chagossian atoll ofPeros Banhos. The move was done in the context of a scientific survey of Blenheim Reef but was regarded as a formal challenge to British sovereignty over Chagos.[68]
On 3 November 2022, the British Foreign SecretaryJames Cleverly announced that the UK and Mauritius had decided to begin negotiations on sovereignty over the British Indian Ocean Territory, taking into account the recent international legal proceedings. Both states had agreed to ensure the continued operation of the joint UK/US military base on Diego Garcia.[69][70]
Whereas these talks included the resettlement of expelled Chagossians, Cleverly's successor as British foreign secretary,David Cameron, later ruled out a return of the islanders.[71]
On 3 October 2024, the UK Government made a joint statement with the Mauritian government that they had negotiated for the sovereignty of the Chagos Islands following two years of negotiation whilst still enabling the running of the American military base on Diego Garcia, thereby ruling out the right of return of the Chagossians to that specific island.[72] The Chagossian people living in the UK have criticised the deal for not having included the Chagossian community in the decision-making process.[73] and expressed concerns that their interests may not be fully safeguarded under Mauritian administration. However, many Chagossians, including those in Mauritius, support Mauritian sovereignty. The Chagos Refugees Group, the largest Chagossian advocacy organization, has been a leading voice for this position. Its leader, Olivier Bancoult, described the UK's decision to return the Chagos Archipelago to Mauritius and allow Chagossians to resettle on the outer islands as a significant step and an acknowledgment of past injustices.[74][75] On the same day, former Maldivian PresidentMohamed Nasheed stated that the decision to hand over the Chagos Islands to Mauritius, despite the Maldives' claims, was unacceptable.[76] On 6 October 2024, theDemocrats Party of the Maldives expressed concern that Maldives PresidentMohamed Muizzu's administration had not been making efforts to assert the Maldives' claim over the Chagos Archipelago, as promised in the presidential pledge.[77] In December 2024, Muizzu sent an official letter to the United Kingdom, which he said asserted the Maldives' strong historical claim to the archipelago, although the specific text of the letter was not released.[78]
There has been a consistent theme of negotiations and decisions about the Chagos Islands being made without directly involving or consulting the Chagossian community. This exclusion from the sovereignty negotiations between the UK and Mauritius has fuelled opposition among Chagossians, who feel their voices have been deliberately ignored in determining the future of their homeland. They demand full inclusion in any discussions or treaties regarding the Chagos Islands.[82]
The Chagossians have been engaged in numerous legal battles over their right to return and the sovereignty of the islands. Legal actions like those initiated by Bernadette Dugasse against the UK government for failing to include Chagossians in sovereignty talks further underscore their opposition to decisions made without their input. This reflects a broader struggle for recognition of their rights and sovereignty over their land.[83]
On 22 May 2025 the Prime Minister of the United Kingdom Keir Starmer signed a formal agreement on the transfer of sovereignty of the Chagos Islands to Mauritius.[84] The British Conservative Party subsequently tabled a motion of censure against the agreement signed on 22 May 2025 between Great Britain and Mauritius.[85]
Under the terms of the deal, the strategic atoll of Diego Garcia and its surrounding 39-kilometre (24 mi) buffer zone are immediately leased back to the UK. This arrangement permits the continued operation of the joint UK/US base on the island for the next 99 years, with an additional 40-year extension and a subsequent right of first refusal.
Mauritius will receive an annual rent of £165 million from the UK for the first three years, followed by £120 million annually for the subsequent ten years. Thereafter, the £120 million annual payment will be adjusted for inflation.[86]
In June 2025, the Great British PAC launched a legal action aimed at demonstrating the illegal actions of the British government in signing this restitution agreement.[87]
Chagossian activists submitted a legal submission to the United Nations Human Rights Committee in June 2025, challenging the legitimacy of the UK-Mauritius deal, arguing that it was negotiated without their consent and perpetuates historical injustices.[88]
On June 10, 2025, UN experts called for the suspension of a recently signed agreement between the United Kingdom and Mauritius, warning that it failed to protect the rights of the displaced Chagossian people. "By maintaining a foreign military presence of the United Kingdom and the United States on Diego Garcia and preventing the Chagossian people from returning... the agreement appears to be in contradiction with the Chagossian right of return," according to the experts. The experts criticized the lack of provisions allowing access to cultural sites or the preservation of the Chagossian heritage. They called on the two countries to renegotiate the restitution agreement, stating, "We call for the suspension of ratification of the agreement and the negotiation of a new agreement that fully guarantees the rights of the Chagossian people".[89]
Following the Chagos Archipelago handover agreement, the British government is also due to introduce legislation to implement the agreement, including amending the British Nationality Act 1981 to reflect that the British Indian Ocean Territory is no longer an overseas territory following Parliament's ratification of the treaty, and to empower the British government to make secondary legislation to allow for the continued operation of the Diego Garcia military base.[90]
On May 23, 2025, India welcomed the agreement between the United Kingdom and Mauritius for the transfer of sovereignty over the Chagos Islands, describing it as an important step in completing the decolonization of the island nation "in the spirit of international law and a rules-based order".[91]
On June 25, 2025, the peers of the House of Lords concluded that the government "cannot ignore" the risk of an "adverse decision" jeopardizing Great Britain's right to operate a joint American and British base.[92]
The agreement may be renewed for an additional 40 years after the initial 99-year period, and for an additional period thereafter.[93]
In July 2025, a legal action demanding that the British government consult with the Chagossians before transferring sovereignty of their territory progressed before the High Court. The judicial review, initiated by Chagossian claimant Louis Misley Mandarin with the support of the Great British PAC, was accepted and fast-tracked by the High Court, with a decision set for July 2025.[94]
Structures on the islands are located in the joint defence andNaval Support Facility Diego Garcia, although the Plantation house and other structures left behind by the Ilois are still standing, however left abandoned and decaying. Other uninhabited islands, especially in the Salomon Atoll, are common stopping points for long-distanceyachtsmen travelling fromSoutheast Asia to theRed Sea or the coast ofAfrica, although a permit is required to visit the outer islands.
The islanders were known as theIlois (a French Creole word for'islanders') and they numbered about 1,000. They were of mixed African, South Indian, Portuguese, English, French and Malay descent and lived very simple, spartan lives in their isolated archipelago working in the coconut and sugar plantations, or in the fishing and small textile industries. Few remains of their culture have been left, although their language is still spoken by some of their descendants in Mauritius.
The inhabitants of Chagos were speakingChagossian Creole, also known as Ilois creole, aFrenchCreole which has not been properly researched[citation needed] from the linguistic point of view.
The Ilois who inhabited the islands were forcibly removed by the US and British governments during the late 1960s and early 1970s – effectively turning the islands into a military base. While a number of islanders had petitioned for the return of their former homes and their right to return has been recognised by the UN General Assembly, the International Court of Justice, and the International Tribunal for the Law of the Sea, the US and UK legal systems have refused to adhere to these decisions, leaving the Chagossians in exile.[95]
Diego Garcia is currently the only inhabited island in the Chagos, all of which compose theBritish Indian Ocean Territory, usually abbreviated as BIOT. The UK considers it anOverseas territory of the United Kingdom, and theGovernment of the BIOT consists of aCommissioner appointed bythe King on the advice of theForeign and Commonwealth Office. The Commissioner is assisted by an Administrator and small staff, and is based in London and resident in the Foreign and Commonwealth Office. This administration is represented in the Territory by the Officer commanding British Forces on Diego Garcia, theBrit Rep. Laws and regulations are promulgated by the Commissioner and enforced in the BIOT by the British Representative.
There are no indigenous peoples living on the island, and the UK represents the Territory internationally. A local government as normally envisioned does not exist.[96] Around 1,700 armed services personnel and 1,500 civilian contractors, mostly American, are stationed on Diego Garcia.[97]
The Chagos, together with the Maldives andLakshadweep, forms theMaldives–Lakshadweep–Chagos Archipelago tropical moist foreststerrestrial ecoregion.[98] The islands and their surrounding waters are a vast oceanic Environment Preservation and Protection Zone (EPPZ) (Fisheries Conservation and Management Zone (FCMZ) of 544,000 square kilometres (210,000 sq mi)), an area twice the size of the UK's land surface.
The deep oceanic waters around the Chagos Islands, out to the 200 nautical mile limit, include an exceptional diversity of undersea geological features (such as 6000 m deep trenches, oceanic ridges, and sea mounts). These areas almost certainly harbour many undiscovered and specially adapted species. Although the deepwater habitats surrounding the islands have not been explored or mapped in any detail, work elsewhere in the world has shown that high physical diversity of the sea floor is closely linked to a high diversity of species.
Thebiodiversity of the Chagos archipelago and its surrounding waters is one of the main reasons it is so special. As of 2010, 76 species that call Chagos home were listed on theIUCN Red List of Threatened Species.[99]
The reefs host at least 371 species of coral including theendemicbrain coralCtenella chagius. Historically, the coral cover was dense and healthy even in deep water on the steep outer reef slopes.[100] Thick stands of branchingstaghorn coral (Acropora sp) previously protected the low-lying islands from wave erosion. Despite the loss of much of the coral in ableaching event in 1998 the recovery in the Chagos was remarkable and overall coral cover increased year on year to 2014.[101] High water temperatures, however, caused coral bleaching in both 2015 and 2016 which resulted in the death of more than two-thirds of corals.[102]
The reefs are also home to at least 784 species of fish that stay near to the shores of the islands including the endemicclownfish (Amphiprion chagosensis) and many of the largerwrasse andgrouper that have already been lost from over-fishing in other reefs in the region.[103]
As well as the healthy communities of reef fish there are significant populations of pelagic fish such asmanta rays (Manta birostris),whale sharks, othersharks, andtuna. Shark numbers have dramatically declined as a result of illegal fishing boats that seek to remove their fins and also as accidental by-catch in the two tuna fisheries that used to operate seasonally in the Chagos.[104]
Seventeen species of breedingseabird can be found nesting in huge colonies on many of the islands in the archipelago, and 10 of the islands have been designatedImportant Bird Areas byBirdLife International. This means that Chagos has the most diverse breeding seabird community in this tropical region. Of particular interest are the large colonies of sooty terns (Sterna fuscata), brown and lesser noddies (Anous stolidus andAnous tenuirostris), wedge-tailed shearwaters (Puffinus pacificus) andred-footed boobies (Sula sula).[citation needed] Land bird fauna is poor and consists of introduced species and recent natural colonisers.Red fody has been introduced and is now widespread.
The remote islands make perfect undisturbed sites for nests of green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles. The populations of both species in Chagos are of global significance given thecritically endangered status of hawksbills and theendangered status ofgreen turtles on theIUCN Red List. Chagos turtles had been heavily exploited for two centuries but they and their habitats are now well protected by the government of the British Indian Ocean Territory and are recovering well.[citation needed]
Coconut crabs are the world's largest terrestrial arthropod and live in one of the most undisturbed populations in the Chagos.
Thecoconut crab (Birgus latro) is the world's largest terrestrialarthropod,[110] reaching more than a metre in leg span and 3.5–4 kilos in weight. As a juvenile it behaves like a hermit crab and uses empty coconut shells as protection, but as an adult this giant crab climbs trees and can crack through a coconut with its massive claws. Despite its wide global distribution, it is rare in most of the areas in which it is found. The coconut crabs on Chagos constitute one of the most undisturbed populations in the world.[111][112] An important part of their biology is the long distances their young can travel as larvae. This means the Chagos coconut crabs are a vital source for replenishing otherover-exploited populations in the Indian Ocean region.[citation needed]
The Chagos Islands were colonised by plants once there was sufficient soil to support them—probably less than 4,000 years. Seeds and spores arrived on the emerging islands by wind and sea and from passingseabirds. The nativeflora of the Chagos Islands is thought to consist of forty-one species of flowering plant and fourferns, as well as a wide variety ofmosses,liverworts,fungi andcyanobacteria.[citation needed]
Today the status of the Chagos Islands' nativeflora depends very much on past exploitation of particular islands. About 280 species of flowering plant and fern have now been recorded on the islands, but this increase reflects the introduction of non-native plants by humans, either accidentally or deliberately. As some of these non-native species have become invasive and pose a threat to the native ecosystems, plans are being developed to control them. On some islands native forests were felled to plant coconut palms for the production ofcopra oil. Other islands remain unspoiled and support a wide range of habitats, including uniquePisonia forests and large clumps of the gigantic fish poison tree (Barringtonia asiatica). Unspoiled islands provide us with the biological information that we need to re-establish the native plant communities on heavily altered islands. These efforts will ultimately help to improve thebiodiversity of the Chagos Islands.[citation needed]
On 1 April 2010 Britain announced the creation of theChagos Marine Protected Area, the world's largest continuous marine protected reserve, with an area of 545,000 km2 (210,000 sq mi).[115][116][117]
This followed an effort led by the Chagos Environment Network,[118] a collaboration of nine leading conservation and scientific organisations seeking to protect the rich biodiversity of the Chagos Archipelago and its surrounding waters. The Chagos Environment Network cites several reasons for supporting a protected area.
The UK government opened a three-monthpublic consultation, which ended after 5 March 2010, on conservation management of the Chagos Islands and its surrounding waters.[119]
On 1 April 2010 the British governmentCabinet established the Chagos Archipelago as the world's largestmarine reserve. At 640,000 km2 (250,000 sq mi), it is larger than bothFrance and the US state ofCalifornia. It doubled the total area of environmental no-take zones worldwide.[40] The protection of the marine reserve will be guaranteed for the next five years thanks to the financial support of theBertarelli Foundation.[120] The setting up of the marine reserve would appear to be an attempt to prevent any repatriation by the inhabitants evicted in the 1960s and 1970s. Leaked US cables have shown the FCO suggesting to its US counterparts that setting up a protected no-take zone would make it "difficult, if not impossible" for the islanders to return. The reserve was then created in 2010.[121]
On 18 March 2015 thePermanent Court of Arbitration unanimously held that themarine protected area (MPA) that the UK had declared around the Chagos Archipelago in April 2010 violated international law.Anerood Jugnauth,Prime Minister of Mauritius, pointed out that it was the first time that the UK's conduct with regard to the Chagos Archipelago had been considered and condemned by any international court or tribunal. He qualified 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 its sovereignty 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 the undertakings became a binding international agreement upon the independence of Mauritius and had 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 were legally binding. The Tribunal also found that the United Kingdom's undertaking to return the Chagos Archipelago to Mauritius when no longer needed for defence purposes was legally binding. This establishes that, in international law, Mauritius has real, firm and binding rights over the Chagos Archipelago and that the United Kingdom must respect those rights. The tribunal went on to hold that the United Kingdom had not respected Mauritius' binding legal rights over the Chagos Archipelago. It considered the events from February 2009 to April 2010, during which time the MPA proposal came into being and was then imposed on Mauritius.[41][42]
On June 10, 2025, UN experts called for the suspension of a recently signed agreement between the United Kingdom and Mauritius, warning that it failed to protect the rights of the displaced Chagossian people. "By maintaining a foreign military presence of the United Kingdom and the United States on Diego Garcia and preventing the Chagossian people from returning... the agreement appears to be in contradiction with the Chagossian right of return," according to the experts. The experts criticized the lack of provisions allowing access to cultural sites or the preservation of the Chagossian heritage. They called on the two countries to renegotiate the restitution agreement, stating, "We call for the suspension of ratification of the agreement and the negotiation of a new agreement that fully guarantees the rights of the Chagossian people".[122]
WikiLeaks published a cable from the US embassy in London to Washington stating:[123]
HMG would like to establish a marine park or reserve providing comprehensive environmental protection to the reefs and waters of the British Indian Ocean Territory (BIOT), a senior Foreign and Commonwealth Office (FCO) official informed Polcouns on May 12. The official insisted that the establishment of a marine park—the world's largest—would in no way impinge on USG use of the BIOT, including Diego Garcia, for military purposes. He agreed that the UK and US should carefully negotiate the details of the marine reserve to assure that US interests were safeguarded and the strategic value of BIOT was upheld. He said that the BIOT's former inhabitants would find it difficult, if not impossible, to pursue their claim for resettlement on the islands if the entire Chagos Archipelago were a marine reserve.
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