Research Briefing
22 November 2022
By Philip Loft

British Indian Ocean Territory:
UK to negotiate sovereignty
2022/23

Summary
1
Background: The UK’s Overseas Territories
2 The creation of the BIOT
3 Removal of Chagossians, 1968-73
4 Legal challenges to UK administration
5 Planned negotiations in 2022/23

commonslibrary.parliament.uk

Number 9673

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

Cover image: NASA Johnson, sts038-086-104 Diego Garcia, November
1990/image cropped/ CC BY-NC 2.0
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Commons Library Research Briefing, 22 November 2022

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

Contents
Summary

4

1

Background: The UK’s Overseas Territories

62

The creation of the BIOT

7

2.1

Mauritian independence and the US military base7

2.2

The question of sovereignty

92.3

The BIOT’s Marine Protection Area (MPA)

93

Removal of Chagossians, 1968-73

11

3.1

How were the population removed?

11

3.2

Many Chagossians are now in the UK

11

3.3

UK funding for Chagossians

12

3.4

Calls to return and UK Government position

13

4

Legal challenges to UK administration

16

4.1

Sovereignty and UK administration

16

4.2

The rights of Chagossians to return

19

5

Planned negotiations in 2022/23

22

5.1

Changing international opinion on the BIOT

22

5.2

Statements on negotiations, November 2022

23

5.3

What policy issues might be considered?

24

5.4

What is the significance of the negotiations for Chagossians?

24

5.5

What might this mean for the US base?

25

5.6

Could Diego Garcia be separated from the rest of the BIOT?

26

5.7

Could there be a co-management agreement?

26

5.8

What does this mean for other Territories whose sovereignty is
disputed?

26

3

Commons Library Research Briefing, 22 November 2022

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

Summary
In 1965, the UK created the British Indian Ocean Territory (BIOT), also known
as the Chagos Archipelago. From 1968 to 1973, it removed the local
population, known as Chagossians or Ilois, for a UK-US military base on the
BIOT’s largest island, Diego Garcia.
Two disputes arose from these events: Firstly, the claim of Mauritius to holdsovereignty over the BIOT and secondly the right of Chagossians to return.
The UK Government has consistently rejected Mauritian claims and said it iscommitted to cede sovereignty when the Territory is no longer needed for
defence purposes. While the Government has apologised for the treatment of
Chagossians, it has concluded a return to be too challenging and expensive.
In November 2022 the UK and Mauritian Governments announced they would
enter into negotiations to resolve “all outstanding issues” on the BIOT. This
follows increasing criticism of the UK at the UN and international courts.
This briefing paper explains the creation of the BIOT, the removal of its
population, legal disputes, and issues for the 2022/23 negotiations.

The creation of the BIOTThe UK took control of the Archipelago in 1814. It was then administered from
Mauritius, a UK colony, until 1965, when the UK created the BIOT through an
Order in Council (a law made by the Privy Council), ruled by a Commissioner.
This followed UK-US negotiations to establish a military base on the BIOT to
counter Soviet and Chinese influence in the region. A 50-year agreement forthe base was signed in 1966 (PDF), and was renewed for 20 years in 2016.
Mauritian Government ministers agreed to the detachment prior to thecountry’s independence in 1968 and accepted UK Government undertakings tocede the Archipelago to Mauritius when no longer needed for defence
purposes. The UK also paid £3 million in recognition of the decision.

The removal of Chagossians
Citing the economic unsustainability of the Archipelago, from 1968 to 1973 theUK removed between 1,400 and 1,700 Chagossians from the BIOT (thoughnumbers are uncertain). Many were resettled in Mauritius, the Seychelles,
and, from 2002, in the UK (PDF). Laws made by the UK’s Commissioner madeit illegal to stay or return without permission.

4

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

The UK has apologised for the nature of their removal, and announced three
payments to support their resettlement, with the most recent in 2016.

Disputed sovereignty
The UK has consistently defended its sovereignty of the BIOT, stating Mauritius
has never held sovereignty over the Archipelago and called for the dispute to
be resolved bilaterally through talks, rather than international courts.
Since the 1980s, Mauritius has advanced its sovereignty claims (PDF) throughinternational fora such as the UN, arguing the UK’s retention of the BIOT
constitutes an unfinished act of decolonialisation (PDF). Most recently, in 2017
the UN General Assembly voted to refer the issue to the International Court ofJustice (ICJ), which in 2019 advised the UK should end control within six
months. A 2019 UN vote called for the UK to adhere to the court’s advice.
The UK Government has said the ICJ advice is not a legally-binding judgment,
and that it would cede the BIOT when no longer needed for defence purposes.

Disputes over the return of Chagossians
There has been litigation by Chagossians in UK courts seeking their right toreturn. The UK Government has commissioned two studies on the possibility of
return, in 2002 and in 2015 (PDF). In 2016, “on the grounds of feasibility,
defence and security interests and cost to the British taxpayer,” theGovernment said a return could not be supported.
Chagossians have challenged the prohibition on their return through the UK
courts—their court victory in 2000 saw the Government repeal the BIOT
ordinances prohibiting their return, but following the 2002 feasibility study(PDF), restrictions were re-introduced in 2004. In 2007, the House of Lords
ruled that the UK Government had the legal power to prohibit their return.

2022/23 negotiations
In November 2022, the UK and Mauritian Governments announced they would
enter into negotiations to resolve “all outstanding issues” on the BIOT,
including sovereignty and the position of the Chagossians. These are intended
to conclude in early 2023.
The Governments have said the operation of the military base will continue.
Mauritian ministers have previously offered the US a 99-year lease for thebase. Mauritius has backed the return of Chagossians to the Archipelago(PDF) in the past but no change has been announced in the UK’s position.

5

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

1

Background: The UK’s Overseas Territories

The British Indian Ocean Territory (BIOT) is one of 14 UK Overseas Territories(OTs). More information on these Territories is provided in the Overseas
Territories Library briefings.
The Territories all have historic links to the UK and with the UK and Crown
Dependencies like Jersey form one undivided realm, where the King issovereign. This means they have no separate representation internationally.
Each Territory is governed separately and has its own constitution. The UK is
responsible for their constitutions, which are made and amendable only by
the UK Privy Council through an Order in Council, rather than local
authorities. These Orders are legal instruments that have the force of law.
Only ten of the 14 Territories are permanently inhabited by British nationals.
For the inhabited OTs, they each have their own parliament and council, as
well as a UK-appointed Governor. The uninhabited Territories, which includes
the BIOT, only have an appointed Commissioner. 1

Map adapted from Foreign & Commonwealth Office, The Overseas Territories, 2012, CM8374, p10

1

6Commons Library, The UK OTs and their Governors and The separation of powers in the UK’s OTs.

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

2

The creation of the BIOT

The BIOT, also known as the Chagos Archipelago, is a collection of 58 islands
in 640,000 square kilometres of the Indian Ocean. Its largest island is Diego
Garcia, which accounts for half its land area. 2
Its nearest neighbours are the Maldives and Sri Lanka. The sovereignty of the
BIOT has long been disputed with Mauritius since the country gained
independence from the UK in 1968 and joined the Commonwealth.
This section provides an outline of the BIOT’s creation, developments since the1960s, including the removal of its population, and disputes over its status.

2.1

Mauritian independence and the US militarybase
The UK took control of Mauritius from France in 1814, during the NapoleonicWars.

UK establishes BIOT in 1965
The islands of the Chagos Archipelago were governed as a dependency of
Mauritius (then a UK colony) until 1965.
In that year, through an Order in Council, the UK combined the islands withsome from the British Seychelles colony, to form the new distinct Territory of
the BIOT. 3
The Order in Council conferred on a non-resident, UK-appointed
Commissioner the power to make laws for the peace, order, and good
government of the BIOT. It made no provisions for an elected assembly. 4

Talks on a UK-US agreement from 1963
The decision to create the BIOT reflected the outcome of negotiations between
the US and UK to establish a military base on the islands.

2
3

4

7

Foreign & Commonwealth Office, The Overseas Territories, 2012, CM8374, p96 and BIOT
Some of the Islands were returned to the Seychelles in 1976 upon its independence by the UK: Peter
Sands, The US and Britain in Diego Garcia: The future of a controversial base, 2009, p5
The BIOT Order 1965, accessed from BIOT Administration, BIOT laws—the ordinances ‘BIOT
constitution orders’Commons Library Research Briefing, 22 November 2022

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

US-UK talks began in 1963, with the US seeking to develop strategic points in
the region in the context of Cold War rivalry and the threat of greater Soviet
and Chinese influence in East Africa and South Asia. The US preferred
uninhabited or lightly populated islands with friendly government for thesebases, in order to minimise local opposition and the threat that the hostgovernment would move closer to the Soviet side in the Cold War. 5
During US-UK talks, the UK Foreign Office recognised these pressures andsuggested transferring control of Diego Garcia to minimise the risk of
opposition:
The Foreign Office clearly indicated that control over the Chagos Archipelago(including Diego Garcia) should be transferred in such way as to minimize
substantially or remove the possibility that use of the islands could be
hampered by external pressures for self-determination. 6

In 1966, the UK came to an agreement with the US to establish a joint militarybase on Diego Garcia, and for the land to be available for this purpose for an“indefinitely long period” (PDF). 7
The initial agreement allowed for a period of 50 years (to 2016) and thepotential for a further 20 years (to 2036—this extension was agreed between
the US and the UK in 2016). 8

UK-Mauritius talks and Mauritian independence, 1968
The UK’s decision to create a separate Territory was taken with theagreement of the Mauritian Council of Ministers, the payment of £3 million
from the UK, and undertaking of the UK “to cede sovereignty of the territory to
Mauritius when it is no longer required for defence purposes.” 9
Following this agreement, Mauritius gained its independence from the UK in
1968, as a member of the Commonwealth.
The UK has consistently argued that Mauritius has “never held sovereignty”
over the BIOT, with the UK holding this continuously since 1814. 10
However, from the 1960s many UN members have argued these acts
constituted a dismemberment of Mauritius and a violation of UN resolutions

5

6

7

8
9

10

8

A. Erickson, W. Ladwig III, J. Mikolay, Diego Garcia and the US’ emerging Indian Ocean Strategy,
Asian Security, 6, 2010, pp214-37, at p221 and Sands, The US and Britain in Diego Garcia, p147
N. D. Howland, Foreign relations of the United States, 1964-68, Volume 21, 2000, documents 33-50,
quote from document 34, 3 March 1964
UK and US Exchange of notes constituting an agreement concerning the availability for defence
purposes of the BIOT, 30 December 1966 (PDF)
HLWS257 [Updated on the BIOT], 16 November 2016
Philippe Sands, The last colony: A tale of exile, justice, and Britain’s colonial legacy, 2022, pp41-3;
International Court of Justice, Legal consequence of the separation of the Chagos Archipelago from
Mauritus: Written statement of the Republic of Mauritius (PDF), 2018, para 2.34, pp63-78; PQ HL1516[BIOT: Sovereignty], 5 July 2022
PQ HL1516 [Chagos Islands: Sovereignty], 19 July 2022

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

calling for the protection of the territorial integrity of states upon achieving
their independence. 11 The UK Government has noted the first explicit Mauritian
claims to sovereignty date from the 1980s (PDF), 12 though Mauritius argues
this reflects its caution when still economically dependent on the UK. 13
For more on legal disputes, see below, section 4.

2.2

The question of sovereignty
Both sides agree that the UK has committed for Mauritius to hold sovereignty
over the BIOT when it is no longer needed for defence purposes.
In 1980, Prime Minister Ramgoolam of Mauritius told the UN General
Assembly that the country reaffirmed its claim to Diego Garcia as the “natural
heritage” of Mauritius and called for the disbandment of the BIOT. He argued
the detachment of the Archipelago had been an unlawful condition imposed
on Mauritian ministers prior to independence (PDF). 14
The UK has argued the Archipelago was ruled as a dependency of Mauritius
prior to independence “as a matter of convenience” and it was “never an
integral part” of the colony. UK Governments have said independence was notgranted on the condition of agreeing to any detachment (PDF). 15
These positions inform the language both sides use—the UK Government says
it will “cede” the Territory to Mauritius when longer needed for defence
purposes, as it argues it was never part of Mauritius, while others state thiswill instead represent the “return” of land over which Mauritius has held
sovereignty.
Section 4.1 provides more on the legal disputes over sovereignty.

2.3

The BIOT’s Marine Protection Area (MPA)
The BIOT’s ocean area is more than twice the size of the UK land area, and it
has around 2,859 square kilometres of coral reef.
On 1 April 2010, the British Government announced that it would establish a
Marine Protection Area (MPA) in the BIOT, where fishing would be banned(apart from Diego Garcia). This was despite opposition from the Mauritian
11
12
13

14

15

9

Philippe Sands, The last colony, pp45-7
Mauritius v United Kingdom, 15 July 2013. Counter memorial submitted by the UK (PDF), pp35-7
Legal consequences of the separation of the Chagos Archipelago from Mauritius in 1965: Statementof Government of Mauritius (PDF), 2018, p121
Legal consequences of the separation of the Chagos Archipelago from Mauritius in 1965: Statementof Government of Mauritius (PDF), 2018, p122
Mauritius v United Kingdom, 15 July 2013. Counter memorial submitted by the UK (PDF), pp12, 23, 27

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

Government, who argued the UK was in breach of international conventions
by establishing the MPA. 16
The UK’s creation of the MPA was challenged by both the Mauritian
Government and by Chagos Islanders.
Mauritius supplied the International Tribunal for the Law of the Sea withevidence suggesting the UK was using the MPA to prevent resettlement.
However, the Tribunal did not accept this evidence, concluding in 2015 that
there was no “ulterior motive or improper purpose.” 17
Section 4 provides more on the associated legal disputes.

16
17

10

Commons Library, The UK’s OTs: Climate change and biodiversity, pp7, 23-24
Chagos Marine Protected Area Arbitration Between the Republic of Mauritius and the UK (PDF), 18
March 2015, para 543

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

3

Removal of Chagossians, 1968-73

In addition to the disputed sovereignty of the BIOT, the second controversy
arising from the creation of the Territory was the removal of its population by
the UK between 1968 and 1973. This means that the Territory has no
permanent population (aside from the military base).

3.1

How were the population removed?
The UK Government has “expressed sincere regret about the manner in which
Chagossians were removed from BIOT in the 1960s and 1970,” but has
concluded their return is now not possible. 18
Most of the population’s ancestors were transported to the Archipelago by
the French in the eighteenth century from Africa to work on plantations.
The numbers living in the BIOT in the 1960s are uncertain, but the current BIOT
Administration estimates between 1,400 and 1,700 people were removed fromthe Archipelago and most went to Mauritius. 19
A 1971 local ordinance, made by the Commissioner, made it illegal to enter orremain in the Territory without a permit. 20
Subsequent orders have reiterated the ban on Islanders returning: British
Indian Ocean Territory (Constitution) Order 2004 and the British Indian Ocean
Territory (Immigration) Order 2004. 21

3.2

Many Chagossians are now in the UK
The number of Chagossians and their relatives in the UK is uncertain, withestimates of between 3,000 and 10,000 people. Many live in Crawley,

18
19
20

21

11

PQ 262406 [BIOT], 13 June 2019
BIOT, BIOT History
BIOT Immigration Ordinance 1971, accessed from BIOT Administration, BIOT laws—the ordinances‘BIOT constitution orders’
Accessible via, BIOT laws—the ordinances ‘BIOT constitution orders’Commons Library Research Briefing, 22 November 2022

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

Sussex. 22 Wythenshawe in Manchester also has around 400 Chagossians,
according to the UK Chagos Support Association. 23
In 2002, the British Overseas Territories Act granted British citizenship to
those resettled from the Chagos Archipelago between 1969 and 1982, andtheir children. 24
In 2022, the UK Government said that applications for the descendants of
those resettled and born outside British Territory would also be allowed from
November 2022. There is a time limit of five years on applications. 25

3.3

UK funding for Chagossians
The UK has paid three amounts of funding to the Chagossians or the Mauritian
Government for their resettlement.

1) Costs of resettlement, 1972
In 1972, the UK paid £650,000 to the Mauritius Government to assist with theresettlement of Chagossians.
This was disbursed with accrued interest in 1977 and 1978 to 595 families.26

2) 1982 agreement and Ilois Trust Fund
Following a 1982 agreement between the UK Government, the Government ofMauritius, and representatives of Chagossians, a further £4 million was paidby the UK into the Ilois Trust Fund for the benefit of Chagossians. The
Government of Mauritius also contributed some land to the Trust Fund andthe Indian Government contributed £1 million. 27
In 2016, the UK Government said 1,344 Chagossians received compensation
through the Fund, mainly between 1982 and 1984. Final disbursements weremade in 1987. 28
According to the European Court of Human Rights, no sums were paid to the
Chagossians on the Seychelles, who numbered around 500 people. 29

22

23
24
25
26
27
28
29

12

The Guardian, Evicted Chagos Islands’ descendants to get British citizenship, 1 September 2022 and
BBC News, Chagos islands cannot return home, says Supreme Court, 29 June 2016
UK Chagos Support Association, Manchester Chagossians community trip, 5 September 2017
British Overseas Territories Act 2002, Section 6
Home Office, Nationality and Borders Bill: Chagossians nationality factsheet, 31 October 2022
PQ 34395 [Ilois: Resettlement], 21 April 2016
PQ 34395 [Ilois: Resettlement], 21 April 2016
PQ 34395 [Ilois: Resettlement], 21 April 2016[2012] ECHR 2094, 35622/04, para 12

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

In 2019, the UK Government said it considered this to be final compensation:
Substantial compensation (around £15.5 million in [2019] current prices) has
been paid to Chagossians since that time. British courts and the European
Court of Human Rights have confirmed that compensation has been paid in fulland final settlement. The Government currently has no plans to review thisdecision. 30

3) Further package of support, 2016-2026
In November 2016, the UK Government announced a support package of £40
million over ten years to support Chagossians in the communities in which
they currently live, primarily the UK, Mauritius and Seychelles.31
This was in response to the Government’s assessment that resettlement of
BIOT could not be supported “on the grounds of feasibility, defence andsecurity interests and cost to the British taxpayer” 32 (see below, page 13 to 15,
for more on potential resettlement).
To November 2021, a total of £810,000 has been spent. 33 Spending focuses on
health, social care, education, employment and culture. 34
Is it compensation?
In 2016, the Government stated the support package “is not compensation”
and instead a “forward-looking” package of support:
We have to look to the future, not the past. Compensation has already been
agreed and upheld in the courts, so we are now trying to offer a forwardlooking support package of £40 million in the manner that I described. 35

The Chagos Support Association similarly said it is not an offer ofcompensation. 36

3.4

Calls to return and UK Government position
Successive UK Governments have said it is not possible for Chagossians toreturn to the BIOT. They cite the continuing need of the Territory for defence
purposes, including the islands around Diego Garcia, and the lack of

30

31
32
33
34

35
36

13

PQ HL14332 [Ilois: Resettlement], 19 March 2019. This is a reference to cases such as thoseconsidered by the European Court of Human Rights in 2012 (PDF)
HLWS257 [Update on the British Indian Ocean Territory], 16 November 2016
HLWS257 [Update on the British Indian Ocean Territory], 16 November 2016
PQ 67088 [Ilois: Finance], 9 November 2021
Foreign, Commonwealth and Development Office, Chagossian support package 2021 to 2022, 9August 2021
HC Deb, 17 November 2016, c931; PQ 2343 [Ilois: Compensation], 10 July 2017
UK Chagos Support Association, Chagossians react to UK Government £40m package, 16 February
2017

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

feasibility of resettlement. 37 The Government’s policy has been challenged incourt—this is discussed in section 4, below.

Government reports and decisions against
resettlement
Several Government-commissioned reports have been conducted.
A 2002 report concluded that rising sea levels and an environment highly
vulnerable to human-induced disturbance made repopulation challenging(PDF) (much of the land is less than one metre above sea level).38 In 2004,
Foreign Secretary Robin Cook said:
Anything other than short-term resettlement on a purely subsistence basis
would be highly precarious and would involve expensive underwriting by the
UK Government for an open-ended period-probably permanently […] it would
be impossible for the Government to promote or even permit resettlement totake place. After long and careful consideration, we have therefore decided tolegislate to prevent it [through the 2004 BIOT orders—see above, 11]. 39

The report’s conclusions have been subsequently criticised, including for its
estimates of changing sea levels on the Archipelago. 40
A further feasibility study was published in 2015. The UK Government said it
was “an important milestone.” 41 The review, carried out by KPMG, considereda range of options for resettlement, and noted that while there would bechallenges, there were “no fundamental legal obstacles” to a resettlement. 42
Following the report, the Government commissioned a consultation on thepotential resettlement of the BIOT, published in 2016.
This found that a majority of the Chagossians who responded were in favourof resettlement in principle (2% were against in all circumstances) but many
expressed concern at how plausible return was, including how accessible jobs
beyond defence and the BIOT administration would be.43
In response to the consultation, the Government said it had decided against
resettlement, on the “grounds of feasibility, defence and security interests,
and cost to the British taxpayer,” citing the challenges of developing modern

37

38

39
40

41
42
43

14

Foreign and Commonwealth Office response to Foreign Affairs Committee Overseas Territories,
Cm7473, 2008, para 16
Royal Haskoning, Agrisystems and MacAlister Elliot For the Foreign & Commonwealth Office,Feasibility study for the resettlement of the Chagos Archipelago, Phase 2B, Volume 1 (PDF) 2002,
pp162-3, 167
Written Ministerial Statement: 15 June 2004, col 32WS
HC Deb, 25 October 2016, 66WH; New Scientist, Chagos islands in sea-level rise controversy, 23
November 2022
Foreign & Commonwealth Office, Policy review of resettlement of the BIOT, 10 February 2015
KPMG, BIOT: Feasibility study report volume 1, January 2015,p2
Foreign & Commonwealth Office, BIOT resettlement policy review consultation, updated 21 January
2016

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

infrastructure, economic opportunities, and the low-lying nature of theislands. It instead pledged additional funding support for the Chagossians(see above, pages 12 to 13). 44

Response to Government policy on resettlement
The All-Party Parliamentary Group (APPG) on the Chagos Islands have been
critical of UK policy.
In response to the Government’s decision in 2016, Andrew Rosindell MP, the
APPG’s Chair, said the decision denied the Chagossians, as British subjects,
the “same rights, freedoms and self-determination that all British citizens
should have” and undermined the UK’s defence of the right to selfdetermination for other OTs, including the Falklands and Gibraltar. 45
Responding for the Labour Party, the Shadow Foreign Secretary, Emily
Thornbury, suggested a pilot programme of resettlement, in line with one ofthe options considered in the KPMG report. 46
The APPG has continued to argue in favour of a pilot resettlement andexploring ways for Chagossians to live and work on the island through thecreation of environmental, scientific and heritage opportunities. 47

Position of Mauritian Government
The Government of Mauritius supports the return of the Chagossians to theArchipelago. In its 2019/20 budget, it allocated around 50 million rupees tosupport any potential resettlement. 48

44
45
46
47
48

15

HLWS257 [Update on the BIOT], 16 November 2022
HC Deb, 17 November 2016, c386
HC Deb, 17 November 2016, c387
Commons Library, Disputes over the BIOT, February 2021 pp9-10
UN Secretary General, Advisory opinion of the International Court of Justice on the legal
consequences of the separation of the Chagos Archipelago from Mauritius in 1965, 18 May 2020
(PDF), para 1.2

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

4

Legal challenges to UK administration

Further reading on legal challenges.
The below provides a non-exhaustive summary of legal challenges,
judgements and advisory opinions relating to the UK’s sovereignty over the
BIOT and the rights of the Chagossians to return.
For more information on these challenges, see:

4.1•

Commons Library, Disputes over the BIOT: A survey, 2013. History of the
BIOT and legal cases to 2013.

•

Commons Library, Disputes over the BIOT: February 2021 update. Legalcases from 2013 to 2021.

•

Philippe Sands, The last colony: A tale of exile, justice, and Britain’s
colonial legacy, 2022. Sands acted as counsel for Mauritius in recent
international cases.

Sovereignty and UK administration2010 Mauritian case against the MPA
In 2010, the UK created the Marine Protection Area (MPA) around the BIOT. In
the same year, Mauritius lodged a case against the MPA under the UN
Convention on the Law of the Sea, arguing the UK had no powers to declarean MPA as it was not a “coastal state” under the Convention in relation to theBIOT. 49
In 2015, the Permanent Court of Arbitration (PCA), which considers a range ofinternational disputes including on maritime boundaries and sovereignty,
unanimously ruled that the MPA declared by the UK was not compatible withobligations under the Convention to give proper regard to the rights ofMauritius and consult with it. 50

49

50

16

An arbitral tribunal constituted under Annex VII of the United Nations convention on the law of thesea in the matter of the Chagos MPA (PDF) March 2015, paras 7-8
As above, paras 528-536

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

It also found that the undertaking to “return the Chagos Archipelago to
Mauritius when no longer needed for defence purposes is legally binding.” 51
However, the Tribunal did not accept evidence from Mauritius that the MPA
was intended as a means to prevent Chagossians resettlement. 52
This ruling is final and binding.
The UK’s position is not that the tribunal’s ruling is tantamount to finding the
MPA unlawful, but rather than the UK should have consulted Mauritius about
its establishment. It said it would be open to bilateral talks. 53

2013-2018 Chagossian case against the MPA in the UK
The Chagos Refugees’ Group argued that the MPA had an improper motive:
namely to make resettlement impractical (due to the ban on fishing) and thatthe consultation on its creation was flawed by the failure to disclose theexistence on the part of Mauritius of inshore fishing rights. 54
Beginning in the High Court, the case reached the UK Supreme Court in 2017.
It endorsed the verdicts of the lower courts that the MPA consultation process
was legal and had not been created for an improper purpose. 55

2019 International Court of JusticeIn July 2016, Prime Minister Pravind Jugnauth announced that Mauritius
would table a resolution at the UN General Assembly seeking to refer theissue of sovereignty to the International Court of Justice (ICJ) for an Advisory
Opinion.
In 2017, the UN General Assembly voted to refer the issue to the ICJ—the UK
said this was an inappropriate use of the mechanism:[It is] an attempt to circumvent the principle that no State should becompelled to have its bilateral disputes submitted for judicial settlement
without its consent, not least on matters of sovereignty. 56

The ICJ issued its Advisory Opinion in February 2019. This said:
The process of decolonization of Mauritius was not lawfully completed in 1968
[…]

51
52
53
54

55
56

17

As above, para 547
As above, para 543
BIOT, Marine Protected Area, accessed 10 November 2022
[2018] UKSC 3 R (on the application of Bancoult No 3) (Appellant) v Secretary of State for Foreign
and Commonwealth Affairs (Respondent) (PDF), 8 February 2018, para 4
As above, paras 49, 63
HCWS10 [BIOT], 16 June 2017

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

The United Kingdom’s continued administration of the Chagos Archipelago
constitutes a wrongful act […]The United Kingdom has an obligation to bring to an end its administration of
the Chagos Archipelago as rapidly as possible […]. 57

The UK Government emphasised that the hearing was an “advisory opinion,
not a judgment,” and that it remained a bilateral dispute with Mauritius that
required a bilateral solution. 58
Mauritian Prime Minister Jugnauth welcomed the court’s statement:
Our territorial integrity will now be made complete, and when that occurs, theChagossians and their descendants will finally be able to return home. 59

In May 2019, the General Assembly, which had requested the advisory
opinion, voted in favour of a resolution calling on the UK to end its
administration of the BIOT within six months. It also called on the UK to workwith Mauritius to facilitate the resettlement of Chagossians who wished toreturn to the archipelago. 60

2021 International Tribunal for the law of the Sea case
In September 2019, the Special Chamber of the International Tribunal for the
Law of the Sea began to consider a case between Mauritius and the Maldives
over a disputed maritime boundary. 61
The Maldives had become involved in the BIOT dispute as its exclusive
economic zone (the sea area for which a state has jurisdiction over marine
resources) overlaps with that of the Archipelago.
The Maldives held that the Tribunal did not have jurisdiction to decide on themaritime boundaries between itself and Mauritius due to the existingsovereignty dispute between Mauritius and the UK over the Chagos
Archipelago. 62
While the Tribunal does not have competence over territorial disputes, it
stated the issue had been considered by the ICJ (see above) and that
“Mauritius’ sovereignty over the Chagos Archipelago can be inferred from the
ICJ’s determinations.” 63

57

58
59
60
61

62
63

18

International Court of Justice, Legal Consequences of the Separation of the Chagos Archipelago
from Mauritius in 1965: Summary of advisory opinion (PDF), 25 February 2019, p12
HC Deb, 26 February 2019, c145
Reuters, World Court- Britain must return Indian Ocean to Mauritius, 25 February 2019
UN, General Assembly welcomes ICJ opinion, 22 May 2019
International Tribunal for the Law of the Sea, Dispute concerning delimitation of the maritime
boundary between Mauritius and Maldives in the Indian Ocean (PDF), 28 January 2021, p1
As above, p2
International Tribunal for the Law of the Sea, Dispute concerning delimitation of the maritime
boundary between Mauritius and Maldives in the Indian Ocean (PDF), 28 January 2021, p4

Commons Library Research Briefing, 22 November 2022

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

In February 2021, the UK Government said it was aware of the Tribunal’s
ruling, and that the UK had not been party to the case. It argued that thestatement:
Can have no effect for the UK or for maritime delimitation between the UK (inrespect of the British Indian Ocean Territory) and the Republic of theMaldives. 64

However, commentators have argued the case has significant implications forthe claims of the UK to patrol the BIOT and management of the MPA. 65

4.2

The rights of Chagossians to return
Legal cases in the UK have generally re-affirmed the decision, and right, of
the UK Government to limit the return of Chagossians to the Archipelago.

1975: Vencatassen claim for compensation
A former resident of the BIOT, Michel Vencatassen, brought a claim against
the UK Government for his forced removal from Diego Garcia in 1971. To avoid
the case coming to court, the UK settled the case for £4 million, to be held in
trust for Chagossians. This formed the basis of the 1982 Trust Fund (seeabove, page 12). 66

1998-2000: Bancoult challenge to 1971 ordinanceprohibiting returns
Olivier Bancoult, one of those forced to leave the Archipelago and leader of
the Chagos Refugees Group, challenged the 1971 immigration ordinance thatprevented the return of Chagossians in the UK High Court in 1998.
In 2000, the High Court found that the powers of the UK Commissioner did notallow for the removal of the islanders.
The Government accepted the verdict, and the Commissioner repealed the1971 ordinance. The Commissioner then introduced a new law which allowed
for entry to the BIOT to those who were an Overseas Territory citizen by virtueof their connection with the Territory, allowing a potential return. 67
However, this decision was later reversed by Orders in Council made by the
UK Government. See Bancoult’s 2004 challenge, below.

PQ 148829 [BIOT: Navy], 8 February 2021
Commons Library, Disputes over the BIOT: February 2021 update, p26
66
Philippe Sands, The last colony, 2022, p68
67[2008] UKHL 61 R (on the application of Bancoult) vs Secretary of State for Foreign & Commonwealth
Affairs, paras 14-18
64
65

19

Commons Library Research Briefing, 22 November 2022

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

2002-2004 Decision on compensation
In 2004, following litigation in the UK, the Court of Appeal affirmed that the £4
million compensation paid in response to the Vencatassen case was the final
sum, with the UK Government having “discharged its obligations to the
Chagossians by payment in full and final settlement.” 68

2004-2008: Bancoult challenge to new orders
prohibiting return
While the Government accepted the High Court judgment in 2000, in 2004 it
made new Orders in Council preventing Chagossians from returning, citing
the costs and environmental challenges this would involve as well as changes
in the international security climate. 69
Bancoult challenged the decision in the High Court, which ruled the Orders
were unlawful and irrational. The Government then appealed to the Court ofAppeal, that in 2007 also found in favour of the Chagossians and thatpreventing their return was unlawful. 70
In 2007, the Government appealed the case to the House of Lords, then the
UK’s highest court. By 3 to 2, the judges ruled in favour of the Government andsaid that it was, through the Privy Council, entitled to legislate for a colony of
the UK. This meant the Orders in Council remained in force. 71
Following the 2008 judgement, the Chagos Refugee Group took the case to
the European Court on Human Rights. In December 2012, the Court ruled theapplication for the case to be considered under the European Convention on
Human Rights was inadmissible. 72

Resettlement decision in the Supreme Court rejected,
2015-16
In 2015 the UK Supreme Court heard an application on the 2008 verdict of theHouse of Lords and dismissed the appeal by a vote of 3 to 2.
However, it did note that it was open for Chagossians to mount a newchallenge in light of the more recent study on resettlement carried out by
KPMG. 73

68
69
70
71
72
73

20

As above, para 21
As above, para 26
As above, para 28
Commons Library, Disputes over the BIOT: A survey, 2013, pp26-7
Commons Library, Disputes over the BIOT: A survey, pp6-8[2016] UKSC 35, R (on application of Bancoult (No2) v Secretary of State for Foreign andCommonwealth Affairs, June 2016, Press summary

Commons Library Research Briefing, 22 November 2022

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

Further review on resettlement rejected, 2019-2020
A judicial review of the Government’s 2016 decision to oppose resettlement
was held in the UK’s High Court in 2019. Its ruling found against the
Chagossians challenge to the decision. 74
The Court of Appeal granted leave to appeal, and judgment was issued in2020. The appeal centred around the applicability of the European
Convention on Human Rights to the BIOT, whether the Divisional Court had
applied the right level of scrutiny to the Government’s decision making, andthe rationality of the decision made by the Government in 2016. The appeal
was dismissed on all grounds. 75
The appellants hoped to appeal to the UK Supreme Court.

74

75

21

[2019] EWHC 221, R (on application of Hoareau and Bancoult) v Secretary of State for Foreign andCommonwealth Affairs (PDF), February 2019, paras 128, 201, 275, 299[2020] EWCA Civ 1010, R (on application of Hoareau and Bancoult) v Secretary of State for Foreign
and Commonwealth Affairs (PDF), July 2020, paras 90, 144, 161, 183

Commons Library Research Briefing, 22 November 2022

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

5

Planned negotiations in 2022/23

5.1

Changing international opinion on the BIOT
United Nations votes
The UK has found itself increasingly isolated over its control of the BIOT at theUnited Nations.
In order for the dispute to be referred to the International Court of Justice(see above, page 17), a majority of UN General Assembly members are
required to vote in favour.
In 2017, 95 countries voted in favour of referral, with 15 against (65abstained). While the UK and the US spoke against, arguing it was a bilateral
dispute, many countries, such as India and the Group of African States,
argued the move was necessary to complete decolonisation. 76
Following the court’s advisory ruling in 2019, only 6 countries (Australia,
Hungary, Israel, Maldives, UK and US) voted against a General Assembly
resolution demanding the unconditional withdrawal of the UK from the
Territory within six months. 116 countries voted in support of the resolution
and 56 countries abstained. 77
The position of the Maldives, which is the nearest state to the BIOT, has also
recently changed, stating in 2022 that it would now vote in favour of a UN
General Assembly motion recognising the Archipelago as part of Mauritius. 78

US and UK’s strategic shift in the region
An additional reason for the new negotiations may be the strategic shift in US
and UK foreign policy towards Asia and the Indo-Pacific in response to China’s
growing economic, maritime, and military power.
Although neither the UK nor Mauritian statement on the new negotiations citea reason for them, 79 analysis by the Carnegie Center argues that territorial
disputes in the Indian Ocean, which also involve France and some of its
76

77

78

79

22

UN, General Assembly adopts resolution seeking international court’s advisory opinion on preindependence separation of Chagos [...], 22 June 2017
UN, General Assembly welcomes international court of justice opinion on Chagos Archipelago, 22
May 2019
The Times of Addu, Attorney General defences stand to recognise Chagos as part of Mauritius, 23
October 2022
HCWS354 [Chagos Archipelago], 3 November 2022

Commons Library Research Briefing, 22 November 2022

British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

former colonies, “open the door for islands to deepen their relationship with
China.” 80Commentators note that resolving a long-standing territorial dispute and apoint of disagreement in international law and UN opinion may form part of
the UK’s attempts to strengthen regional alliances against China. 81

5.2

Statements on negotiations, November 2022
On 3 November 2022, the Foreign Secretary, James Cleverly, announced that
the UK would enter into negotiations with Mauritius to resolve “alloutstanding issues” relating to the BIOT. This includes the exercise ofsovereignty. 82
He said the agreement would be made based on international law and take
into account relevant legal proceedings and include issues relating to theformer inhabitants of the Archipelago.
This announcement followed bilateral talks between the UK Prime Minister, Liz
Truss, and Prime Minister Jugnauth at the UN General Assembly earlier in
2022.
The Governments are entering negotiations with a view to achieve anagreement in early 2023. 83
Speaking the same day, the Mauritian Prime Minister, Pravind Kumar
Jugnauth, made a similar statement and undertakings (PDF) to the country’s
National Assembly.84

Past talks have not succeeded
These are not the first talks between the UK and Mauritian Governments:
Talks took place in 2009 but ended following the UK’s creation of the MPA in
2010, which the Mauritian Government had criticised as a unilateraldecision. 85
Further rounds of talks also took place in 2016 and 2017, but this did not
progress and ended when Mauritius sought a vote of the UN General
Assembly to refer issue of sovereignty to the ICJ.86

80

81
82
83
84
85
86

23

Carnegie Endowment for International Peace, We’re thinking about the Indian Ocean all wrong, 2
May 2022
Peter Harris, Want a rules-based order for the Indo-Pacific? Start with Diego Garcia, 8 January 2021
HCWS354 [Chagos Archipelago], 3 November 2022
HCWS354 [Chagos Archipelago], 3 November 2022
National Assembly, Hansard 3 November 2022, pp19-20 (PDF)
Commons Library, Disputes over the BIOT: A survey, May 2013, p14
Commons Library, Disputes over the BIOT: February 2021 update, pp15-16

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

5.3

What policy issues might be considered?
The UK Government’s written statement sets out several priorities fornegotiations:•

Strengthen relations with Mauritius and work together on regional andglobal challenges.

•

Increase cooperation on Indian Ocean security, maritime security, andmarine protection.

•

Conserve the environment•

Tackle crime, including illegal migration, fishing, drugs and arms
trafficking.

The issue of UK sovereignty over the BIOT was last considered by the Foreign
Affairs Committee in 2008, when it recommended the UK should take theviews of Chagossians into account when seeking a resolution to thesovereignty dispute (PDF). 87
The Foreign Office said the views of other parties would be welcome, though
any negotiations would be between the states concerned. 88

5.4

What is the significance of the negotiations for
Chagossians?
The UK Government has not made any statements on the position of
Chagossians, other than this will be one of the outstanding issues it intends toresolve. 89
Responding to the November 2022 announcement, Human Rights Watch has
said the participation of Chagossians should be prioritised, and a form of
reparations and compensation arranged. 90
The UK Government previously argued that the Islands could not be resettled
on the grounds of feasibility, defence and security interests, and the cost to

87

88
89
90

24

Foreign and Commonwealth Office response to Foreign Affairs Committee Overseas Territories,
Cm7473, 2008, recommendation para 41 (PDF)
As above, para 129-30
HCWS354 [Chagos Archipelago], 3 November 2022
Human Rights Watch, Chagos Islands: Include long-expelled residents in negotiations, 8 November
2022

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

the UK taxpayer (see above, page 14). 91 No change of the Government’s
position has been published.

5.5

What might this mean for the US base?
UK-US agreement lasts until 2036
In 2016, the UK renewed the agreement for the joint military base until 2036. 92
The Foreign Secretary, James Cleverly, has said maintaining US and UK
influence in the region is “at the heart of the British negotiations.” 93

Undertakings of Mauritian Government
Mauritius has sought to issue assurances that the base would be unaffectedby any change in control.
There had been reports that the US was considering Australia’s Cocos Islands
as an alternative to the BIOT, prior to the 2016 renewal.94 While the US has
been using the islands for some time, analysts stress that they lack key air
and port infrastructure and there may be political opposition. 95
In 2012, Prime Minister Navin Ramgoolam said Mauritian sovereignty could beestablished without prejudice to the use of Diego Garcia as a military base.96
In 2020, Mauritius offered the US a 99-year lease for its Diego Garcia base,97
and current Prime Minister Jugnauth said in 2021 that the end of any UKadministration over the BIOT would have “no implications for the US militarybase,” which his country “is committed to maintain.” 98
In November 2022, the UK Government said any agreement will ensure thecontinued operation of the joint military facility on Diego Garcia. 99

Foreign & Commonwealth Office, BIOT resettlement policy review consultation, updated 21 January
2016
92
HLWS257 [Update on the BIOT], 16 November 201693
Foreign Affairs Committee, Oral evidence: Work of the FCDO, 14 November 2022, Q254
94
Reuters, Australia open to US spy flights from Indian Ocean Island, 28 March 201295
The Diplomat, Australia’s Cocos Islands cannot outpace America’s troubled Diego Garcia, 16 April
2019
96
All Africa, Mauritius: Diego Garcia—The case, sovereignty and right of return, 18 June 201297
Nikkei Asia, Mauritius makes play for future with US base on Diego Garcia, 18 November 2020
98
BBC News, UN court rules UK has no sovereignty over Chagos islands, 28 January 2021
99
HCWS354 [Chagos Archipelago], 3 November 2022
91

25

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

5.6

Could Diego Garcia be separated from the restof the BIOT?
Some islands in the BIOT were ceded to the Seychelles in 1976 upon its
independence from the UK, as they were not needed for defence purposes.
Some UK Parliamentarians have suggested the “transfer of the Outer Islandsof the British Indian Ocean Territory to Mauritius,” arguing they are notneeded for defence purposes. 100
However, in 2019 the UK Government said the outer islands are too small andundeveloped to sustain habitation and are “integral” to the effective
operation of the defence facility on Diego Garcia. 101

5.7

Could there be a co-management agreement?
The BIOT is not the only disputed Territory in the Indian Ocean, with France
holding several islands.
In 2010, France agreed a co-management agreement with Mauritius over the
French-held Tromelin Island. The agreement allows the co-management of
the Island, including over its economy and management. The agreement did
not prejudice any sovereignty claims over Tromelin. 102
If applied to the BIOT, this could include, for example, joint management over
the MPA.

5.8

What does this mean for other Territories
whose sovereignty is disputed?
The BIOT is not the only Territory that has seen the UK’s sovereignty
challenged, with Argentina and Spain claiming sovereignty over the Falklands
and Gibraltar, respectively. The UK rejects claims with both and cites the
support of the local populations in remaining a UK OT.
Since the November announcement, Argentina’s foreign ministry has called
for talks over the Falklands. 103

100
101
102
103

26

As suggested, for example: PQ 138065 [BIOT], 21 March 2022; HL Deb, 27 January 2022, c491
HC Deb, 3 July 2019, 586WH and PQ242056 [BIOT] 16 April 2019
Sean Murphy, International law relating to islands, 2019, p145
Buenos Aires Times, Argentina urges UK to resume talks over Malvinas Islands sovereignty, 3
November 2022

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British Indian Ocean Territory: UK to negotiate sovereignty 2022/23

However, the Falkland Island’s Governor, Alison Blake, said the UK-Mauritius
negotiations do not represent any broader shift in UK policy towards its
Territories:
UK ministers are very clear that this does not represent a broader shift in UK
policy towards the Falkland Islands, which is a modern relationship based on
partnership, shared values and the right of the Falkland Islanders to determine
their own future. 104

The Falkland Island’s Legislative Assembly has issued a similar statement. 105
Gibraltar’s Government also says it has no concerns: In November, Chief
Minister Fabian Picardo said the UK’s commitment to Gibraltar is unaltered:
In the case of Gibraltar the United Kingdom has made a cast iron commitment
not to transfer sovereignty against the wishes of the people of Gibraltar andnot even to start a process of sovereignty discussions with which theGibraltarians are not content
The Government of Gibraltar will never consent to any such discussions ofsovereignty ever commencing. 106

Further reading on the Falklands and Gibraltar•

Lords Library, Sovereignty since the ceasefire: The Falklands 40 years on,
August 2022•

Commons Library, Brexit and Gibraltar, May 2017. Includes discussion of
Spanish claims to Gibraltar and the Gibraltar and UK Government
response.

Merco Press, Chagos: Mauritius and UK agree military base on Diego Garcia will remain, says
Foreign Secretary, 5 November 2022
105
Merco Press, Falkland Islands Legislative Assembly reaffirms rights to self-determination amid
Chagos sovereignty negotiations, 4 November 2022
106
Gibraltar Chronicle, Britain agrees to sovereignty talks with Mauritius over Chagos Islands, 3November 2022
104

27

Commons Library Research Briefing, 22 November 2022

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