3.1.1 – The State and Globalisation
The Chagos Islands are an Archipelago in the Indian Ocean. They comprise more than 60 individual islands and their sovereignty has long been under dispute. In October 2024, Britain reached an agreement with Mauritius to return the Islands – the culmination of a long and bitter legal dispute. For a long time, in spite of numerous legal rulings, it did not appear the sovereignty of the islands would change. As such, it is a very good example of the soft nature of international law which is one of the fundamental weaknesses of the international legal system.
What is the history of the Chagos Archipelago?
The French were the first great power to stake a claim to the islands in the 18th Century. At the time the islands were entirely uninhabited. However, after Napoleon’s defeat in 1814, the islands were ceded to Britain as part of the Treaty of Paris. The Islands were administered from Mauritius, which was also ceded to Britain as part of the treaty.
From 1840 onwards the islands became permanently inhabited. Most of the inhabitants were descended from slaves, however, they were freeman. This remained the status quo on the islands for a century.
By the 1960s British decolonisation was advancing rapidly and it was clear that British control of Mauritius was coming to an end. However, the geographical position of the Chagos Islands in the Indian Ocean made them strategically valuable. This was particularly the case as Britain was dealing with the loss of her empire East of Suez and was trying to remain a global power. Therefore, the British Government paid Mauritius £3 Million Pounds in in 1965 to purchase the Chagos Islands. The purchased islands were renamed the British Indian Ocean Territory.
Over the next five years, Britain forcibly depopulated the islands. This was done in secret and without international knowledge. By 1973 the entire population of around 2,000 Chagos Islanders had been removed from the islands and the inhabitants were moved to Mauritius, a state that most islanders had never set foot on before.
What was the interest of the United States in the Chagos Islands?
In 1971 Britain and the United States signed a treaty which gave the US a leasehold over the islands in order to build a Naval and Air Base. The US saw this deal as essential in limiting Soviet influence in the Indian Ocean. As part of this agreement the British Government received significant discounts on the Polaris Nuclear Weapons system which formed the basis of Britain’s nuclear deterrent until 1996 when it was replaced with Trident.
At the end of the Cold War the base at Diego Garcia remained strategically important. For example, the base is just 3,008 miles from Iran and is a similar distance to Afghanistan, Pakistan and much less to India. The base gives the US strategic options and has been describe as an ‘unsinkable aircraft carrier’ with numerous military operations launched from it – including during both Gulf Wars and during the War on Terror.
What is the dispute over the Islands?
In the 1980s Mauritius claimed sovereignty of the islands. They contended that the 1965 separation was illegal under international law and there began some international pressure began to grow on Britain to give up sovereignty of the islands. In recent years the dispute has escalated significantly. In 2010 the UK Government declared a Marine Protection Area (MPA) around the Islands. It is currently the world’s largest Marine Protection Area.
Marine Protection Areas are set up to provide environmental protections for areas of the ocean. They are created to protect wildlife or to create oceanic research areas. However, they may also have a strategic imperative as they place legal limits on ships or aircraft entering the established zone. Notably, classified diplomatic correspondence between the UK and US released by Wikileaks in 2010 clearly indicate that an ulterior motive in the creation of the MPA might be to prevent Chagos Islanders from re-inhabiting the Islands:
“ Establishing a marine reserve might, indeed, as the FCO’s Roberts stated, be the most effective long-term way to prevent any of the Chagos Islands’ former inhabitants or their descendants from resettling in the [British Indian Ocean Territory]”
What legal action has been taken in UK Courts?
In 2006 Chaggosians won a case in the U.K. High Court that would enable them to return to the Chagos Islands but the decision was immediately appealed by the UK Government. The Court of Appeals agreed with the High Court but again the U.K. Government appealed the decision, so it went to the Appellate Committee of the House of Lords (Law Lords), then the highest court in the U.K.
In 2008, the Law Lords ruled 3-2 in the Government’s favour ending the Chagossians hopes of returning. The ruling by the Appellate Committee stated that the Human Rights Act (1998) had no jurisdiction in the British Indian Ocean Territory (Chagos Islands) as the BIOT is not part of the United Kingdom and therefore, alongside other reasons, dismissed the appeal.
What legal action has been taken in international courts?
In 2015 Mauritius launched action against the British Government under the United Nations Convention on the Law of the Sea. The Government of Mauritius argued that the Marine Protection Area was illegal under the UN Convention. The Permanent Court of Arbitration is located at The Hague. The PCA is not a UN institution, but is utilised by UN Members as a place to resolve international disputes and its opinions are given legal weight.
In March 2015 the PCA ruled that Britain had indeed acted unlawfully by creating the Marine Protection Area. This was a blow to Britain’s international credibility, but had no binding legal effect whatsoever.
Following this, the case was debated by the United Nations General Assembly and in June 2017 the Assembly voted to refer the case to the International Court of Justice. The ICJ is the judicial arm of the United Nations and it is sometimes informally called the ‘World Court’. The ICJ has cases referred to it by the UNGA and is composed of a panel of 15 judges who are elected by the UNGA for nine year terms. The judgements of the ICJ are only advisory, however, as the foremost international court arbitrating disputes between states it is the most authoritative body in international law.
In February 2019 the International Court of Justice judged that the separation of the Chagos Islands from Mauritius in 1965 had been illegal and determined that the territory should be returned to Mauritius as soon as practically possible. The ruling of the court stated that:
“the process of decolonization of Mauritius was not lawfully completed when that country acceded to independence…the United Kingdom is under an obligation to bring to an end its administration of the Chagos Archipelago as rapidly as possible”
The main reason that the court came to this judgement was that the deal was a violation of UN Resolution 1514 from 1960 which specifically banned the breakup of colonies into different territories as a condition of independence being granted.
In response to the ICJ ruling the UK Government refused to comply. When asked about the issue in the House of Commons in May 2019 the Minister for Africa said:
“…the Chagos archipelago has been under continuous British sovereignty since 1814…The whole world benefits from the security provided by having this base in the Indian Ocean”
In January 2021 the UN’s International Tribunal for the Law of Sea concluded, in a case focusing on Mauritius and Maldives, that the UK had no sovereignty over the archipelago and that Mauritius was sovereign there.
Why did Britain agree to a return of sovereignty to Mauritius in October 2024?
In October 2024 it was announced that Britain would cede sovereignty of the Chagos Islands to Mauritius. A joint statement between the UK and Mauritian governments said:
‘The Prime Minister of the Republic of Mauritius and the Prime Minister of the United Kingdom of Great Britain and Northern Ireland today confirm that they have reached an historic political agreement on the exercise of sovereignty over the Chagos Archipelago.
Following two years of negotiation, this is a seminal moment in our relationship and a demonstration of our enduring commitment to the peaceful resolution of disputes and the rule of law. Negotiations have been conducted in a constructive and respectful manner, as equal sovereign States, on the basis of international law, and with the intention of resolving all outstanding issues between the United Kingdom and Mauritius concerning the Chagos Archipelago, including those relating to its former inhabitants.’
As part of the deal, Britain and America will retain on Diego Garcia, the site of their airbase, with a 99-year lease agreed with the government of Mauritius.
The decision of the British Government is clearly a response to the global political pressure that came from the adverse rulings and judgements from the ICJ and the UNGA. It is clear, however, that without an agreement on Diego Garcia this agreement would not have been reached. Britain was not willing to put international law ahead of its strategic interests. However, when a balance could be found between these considerations, it was able to make the final decision to cede the territory. Clearly, as a prominent liberal democracy, being in constant contravention of international law was not a position Britain wanted to be in.
However, domestically, this has not been a popular decision. Both the Conservatives and Reform UK have criticised the UK Government. In January 2026, the Government lost four votes in the House of Lords on the issue, including one calling for a referendum of Chagossians to see if this was their desired wish.
What does this case indicate about the strength of international law?
Despite the eventual outcome, this case highlights one of the fundamental limits of the International Court of Justice – the decisions it makes are not binding, they simply add to the canon of International Law and, at times, put pressure on Governments to consider their policies. However, they rely on other institutions to carry out any ruling they give.
Pressure on the U.K. grew in May 2019 when the UN General Assembly voted by 116-6 to condemn the British ‘occupation’ of the Chagos Islands. The US, Hungary, Israel, Australia and the Maldives were the only countries to back the UK’s stance on the Islands. Even the then Pope, Francis, voiced his concerns during an Indian Ocean visit:
“ You must obey international institutions. That is why the United Nations were created. That’s why international courts were created.”
However, the motion, this time from the General Assembly, was not binding. There was still no legal impetus for Britain to take positive action and it has consistently refused to recognise the claim of Mauritius to the islands.
For a long time, Britain showed little sign of vacillating on the issue and knew they had the unwavering support of the US. This does highlight some of the fundamental weaknesses of the UN and other intergovernmental organisations:
- Motions are rarely binding. They rely on self enforcement. When major powers are the subject of criticism, little is likely to force them to relent.
- International Law is still widely disputed and despite Liberal intentions, it cannot be consistently enforced.
Yet, it also shows that these institutions can still be influential as a forum of global opinion. Britain had to consider the long-term impact of a failure to comply with international law and therefore the impact on its moral position in the world.
Article Summary
Britain has for a long time been in a territorial dispute over the Chagos Islands. Despite numerous adverse legal rulings, including from the International Court of Justice, Britain appears entirely unwilling to countenance surrendering sovereignty of the islands due to their strategic importance and the impact it would have on their relationship with the United States. As such, it is a good example of soft nature of international law and the limits of international legal institutions.
Key Terms
Decolonisation – The process where states give up the remnants of their empires.
Sovereignty – The state of having power or control over something.
Wikileaks – A website launched in 2006 that published leaked classified information about states including the US.
High Court – A senior court in the UK which hears significant judicial review case.
Appellate Committee of the House of Lords – The former supreme court of the UK which was based in the House of Lords and sat upon by the Law Lords.
Permanent Court of Arbitration – A non-binding arbitration court that was founded in 1899 and based in the Hague, Netherlands.
United Nations General Assembly – The main deliberative body of the Untie Nations which is based on sovereign equality between states.
International Court of Justice – The judicial arm of the United Nations. Its weakness its reliance on the UN Security Council to enforce its resolutions.
Last Updated – 09.01.26