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Disputes over the British Indian Ocean Territory: August 2018 update

Published Wednesday, August 22, 2018

This briefing describes the main developments since mid-2013 in long-running disputes over the British Indian Ocean Territory (BIOT).

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Between 1968 and 1973 the British Government cleared the entire Chagos Archipelago of its inhabitants, in anticipation of a US military base on the biggest island, Diego Garcia. The Archipelago was made a colony, the British Indian Ocean Territory (BIOT). It subsequently became a British Overseas Territory.

Two main disputes have arisen from these events. One has been between the Chagos Islanders and the British Government over the legality of their removal and whether they have a right to return. The other has been between the UK and Mauritius about sovereignty over the BIOT. In 1965 the UK undertook that it will cede sovereignty to Mauritius once the BIOT is no longer required for defence purposes.

A May 2013 Library briefing surveyed the origins and subsequent evolution since 1965 of these disputes, including past and ongoing legal cases brought before British, European and international courts. This update summarises the main developments since May 2013.

In June 2015 the Supreme Court heard an application for the 2008 verdict of the House of Lords – which ruled that the use in 2004 of Orders in Council to prevent the Chagossians from returning had been lawful – to be set aside. In June 2016 the Supreme Court ruled against the application by a majority of 3 to 2. But, with a fresh resettlement feasibility study recently completed, it also said that the Government should reconsider the ban on the Chagossians returning home as it may no longer be lawful.

However, in November 2016 the previous Government announced that it had decided not to allow resettlement. The decision provoked condemnation from Mauritius and supporters of the Chagossian cause in the UK and is now the subject of judicial review. The hearing is scheduled for December 2018.

There has also been ongoing debate about the best use of – and motives behind – a £40 million support package for Chagossians that was announced when the decision was made, as well as renewed calls for the restoration of the right of abode, perhaps as a prelude to a change of policy on resettlement. There have been three Chagossian ‘heritage visits’ to BIOT over the last year, although some sections of the community have been boycotting the visits.

In 2015 a Marine Protected Area (MPA) introduced by the British Government around the Chagos Archipelago (apart from Diego Garcia, where there is a US military base) was ruled by a Tribunal under the UN Convention on the Law of the Sea to have been established without proper regard to the rights of Mauritius. Some legal commentators have taken this as tantamount to saying that the MPA is unlawful. The UK disagrees with this interpretation.

The UN Tribunal was more equivocal on sovereignty than the Mauritian Government, which brought the case, hoped it would be. It declined jurisdiction on the issue but found that the UK’s 1965 undertaking to cede sovereignty to Mauritius when the BIOT is no longer required for defence purposes is binding under international law.

In July 2016 Mauritius said that it would seek a referral by the UN General Assembly to the International Court of Justice later in the year in order to obtain an advisory opinion on sovereignty. It went ahead and did so in June 2017. The General Assembly voted 94-15 to refer the issue. The Court has collected written submissions and is holding public hearings on 3-6 September 2018. It is not expected to issue an opinion until 2019.

Chagossians in the UK have been seeking to challenge the establishment of the MPA through the English courts since 2013. They argued that it was created for an improper purpose – to prevent resettlement – and that the consultation process prior to its establishment had been inadequate. However, the High Court and Court of Appeal found against the Chagossians and in February 2018 the Supreme Court did so too.

A decision on whether to extend the life of the US military base on Diego Garcia for a further 20 years had to be made by the end of 2016. A decision to do so was announced in November 2016.

In January 2018, Henry Smith introduced the British Indian Ocean Territory (Citizenship) Bill in the UK Parliament. It seeks to allow anybody who is descended from Chagossians born in BIOT to become British Overseas Territories Citizens. At present, only Chagossians born in BIOT and the first generation that was born in the UK can do so. The second reading is due in October 2018. The Government has not yet confirmed what its position is on the Bill.


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