The British Indian Ocean Territory Constitution Order 2004 is legislation made by Royal Prerogative. Section 9 provides that there is no right of abode in the Chagos Islands. In R (Mandarin) v HM BIOT Commissioner (31 March 2026) the British Indian Ocean Territory Supreme Court ruled that section 9 was irrational and quashed it. I argue that the judgment is correct, that the 2004 Order is a colonial anachronism and that is antithetical to constitutional principles, democratic principles and the rule of law.
Legal overview of BIOT
Former UK Foreign Secretary Robin Cook described government action relating to the Chagos Islands as “sordid and morally indefensible”. The Chagos Islands became British Indian Ocean Territory (BIOT) in 1965 when the UK detached it from Mauritius. Mauritius gained independence from the UK in 1968. In 1966 the UK Government had entered into a defence agreement granting the US rent-free access to the Chagos Islands, initially to develop a facility on one of the islands, Diego Garcia. Between 1968 and 1973 the entire island population was forcibly removed by the new BIOT Administration. The Immigration Ordinance 1971 (BIOT legislation) prohibited a person from entering or remaining in BIOT. In subsequent years Diego Garcia has been transformed into one of the US military’s most important overseas bases.
In Bancoult (No 1) [2001] QB 1067 the UK courts ruled the 1971 Ordinance void. In 2004 the BIOT Constitution Order and Immigration Order were enacted. Section 9 of the Constitution Order is the key provision:
No right of abode in the Territory
9. — (1) Whereas the Territory was constituted and is set aside to be available for the defence purposes of the Government of the United Kingdom and the Government of the United States of America, no person has the right of abode in the Territory.
(2) Accordingly, no person is entitled to enter or be present in the Territory except as authorised by or under this Order or any other law for the time being in force in the Territory.
The accompanying Immigration Order 2004 provided administrative processes for granting permits and facilitating removals. Throughout the subsequent decades Chagossians again challenged these Orders in the English Courts, culminating in Bancoult (No 2) [2009] UKHL 61 where the House of Lords by majority verdict ruled these Orders valid. Mauritius pursued its sovereignty claim in the UN, leading to an Advisory Opinion in the International Court of Justice in 2019 ruling against the UK. As a result of international legal and political pressure, in 2025 the UK Government entered into a treaty to return BIOT to Mauritius. A leasing agreement for Diego Garcia to remain under UK control protects the operation of the US military bases on Diego Garcia for 99 years on payment of annual ‘rent’ to Mauritius. A Government Bill to give effect to this treaty is currently before Parliament. Given this history of the UK’s attempt at 20th Century colonial deviousness, it is hard to disagree with Bruce Kent’s view that this “is a story of ruthless military and economic imperialism, Cold War driven, and underpinned by servile British governments”.
On 31 March 2026, James Lewis KC sitting as Chief Justice of BIOT in the BIOT Supreme Court (equivalent to the English High Court) considered a case arising from a number of persons (including some with Chagossian heritage) who landed on one of the outer islands of BIOT without permission. He gave judgment stating that:
“any rational reason for passing the provision [section 9] has now disappeared, if there ever was one. A claimed power to exclude a whole population must be justified by legal source, not administrative necessity. The 2025 Treaty … removes any claimed reliance on defence or security issues in repopulating the outer islands, as well as rendering funding issues otiose.” [para 169]
Section 9 of the Constitution Order 2004 was quashed. There is now no legal basis for denying the right of abode on the outer islands. The judgment did not expressly refer to Diego Garcia (which is not an outer island), so presumably the Immigration Order 2004 still applies and a person could still be removed from Diego Garcia on its authority.
Critique of the Constitution Order 2004
The Constitution Order 2004 was made in exercise of the Royal Prerogative. Legislation made by Royal Prerogative is an historical anachronism. It is legislation made by the monarch on the advice of the Privy Council. Dicey described prerogative power as the residue of discretionary or arbitrary authority left in the hands of the Crown and traced its source back to the Norman Conquest. In practice prerogative legislation is made by a UK Minister. It is primary legislation but does not have parliamentary authority. It is legislation made without a legislature on the basis of ancient monarchical rights. I have previously referred to it as a paradigm of bad law-making.
My first criticism of the 2004 Order is that it breaches constitutional norms. A constitution sets out the relationship between the governed and the governors. Elkins sees its purposes as being to limit the behaviour of government, to define the nation and its goals, and to define authority and set up government institutions. Banishing the governed from living in the territory cannot be seen in any way as falling within this definition of a constitution. The only relationship it envisages with the governed is their removal. As Lord Mance pithily put it in Bancoult (No 2) “a constitution which exiles a territory’s inhabitants is a contradiction in terms” [para 157]. This is a modern-day continuation of high-handed and racist government policies of the colonial era. As recently as 2009, the BBC reported a WikiLeaks allegation that UK diplomats had referred to there being no “Man Fridays” on the islands. This is not a one-off: Mandarin referred to an infamous record from a 1966 colonial official: “The object of the exercise was to get some rocks which will remain ours; there will be no indigenous population except seagulls who have not yet got a committee (the Status of Women Committee does not cover the rights of birds)” [para 19].
My second criticism of the 2004 Order is that it is profoundly undemocratic. Although there are many different definitions of democracy, at heart it is a simple concept that the people elect their representatives, and those representatives make the law for them. This applies in the UK and also in the British Overseas Territories (OTs). Additional considerations do apply to basic democratic principles in the OTs: there are generally some matters that are reserved to the UK Government (or the Governor or Commissioner as the representative of the Crown). These are generally matters like international relations or national security. In a review of the system of ministerial government in the British Overseas Territory of St Helena in which I participated, we stressed the importance of elected local ministers enacting legislation for the benefit of residents: “St Helenians … are the people best placed to make decisions about what happens on St Helena” [para 10]. This is in line with current FCDO guidance that “powers are devolved to the elected governments of the Territories to the maximum extent possible consistent with the UK retaining those powers necessary to discharge its sovereign responsibilities”. This democratic principle was completely ignored in the enactment of the Constitution Order, as it was in previous prerogative legislation removing the Chagossians.
My third criticism of the 2004 Order is that it undermines the rule of law. Adam Tomkins describes prerogative legislation as “unaccountable, indeed wholly secret rule-making”. The only place that BIOT legislation is required to be published is in the BIOT Gazette – seen as a positive by a Legal Adviser to the Foreign Office in 1971 who stated that it has “only very limited circulation … Publicity will therefore be minimal”. In 2013, the BIOT Gazettes were not available online, and had a circulation list of 20, 16 of which were various emanations of government, the other 4 being UK based law libraries. The 2004 Order was deliberately kept from the Foreign Affairs Committee in advance of being made. Jack Straw, then Foreign and Commonwealth Secretary explained this by letter of 9 July 2004: “we needed to preserve confidentiality if we were to avoid the risk of an attempt by the Chagossians to circumvent the Orders before they came into force”.
In 2013 I catalogued the tremendous difficulties in finding an actual copy of the 2004 Order anywhere. I literally went through dusty archives in the basement of the library of the Institute of Advanced Legal Studies at the University of London to find one. As of 2ndApril 2026, the only online database of BIOT legislation is maintained by Richard Dunne, a lawyer who was involved in the Bancoult litigation in the 2010s. This is not an official government website. According to the UK Government, the BIOT website contains “all the current legislation for the Territory”. This is not true. If one looks at the BIOT website under the heading of Legislation, the 2004 Constitution Order is not there, either under the heading of Gazettes, Orders in Council, Ordinances, Regulations or King’s Proclamation. This is a deliberate policy, reminiscent of Operation Legacy, another colonial policy to cover up abuse.
An element of the rule of law is accessibility of legislation. One of the ways that Lon Fuller’s mythical King Rex failed to make law is that the contents of the law would remain a state secret, known only to Rex. The Venice Commission said that “the state must make the text of the law easily accessible”. The Office for Democratic Institutions and Human Rights, published Principles of Democratic Lawmaking and Better Laws in 2023. (Disclaimer, I was a member of the working group.) Principle 17 is that legislation “should be easily and publicly accessible for the entire population”. Deliberate concealment of the 2004 Order undermines the rule of law.
Two further points arise from the case. The first is the use of what may be termed justificatory clauses in legislation. Section 9 seeks to justify the exile of the population by claiming that the territory was constituted for defence purposes. The judge stated [para 167] “It is unusual to see the purpose for a provision embodied in the provision itself, they are not in a recital, but in my judgment that simply reinforces the force necessary to remove a fundamental right.” Section 9 isn’t quite a purpose clause. It isn’t quite a recital of the sort that one would find preceding EU legislation. Nor is it quite a preamble one would find at the start of old UK Acts. It is more an attempt to make something a legal fact by stating it in legislation, something that, in a different context, Adam Tuckercharacterised as “a legal fiction.” The difficulty with this kind of justificatory clause is when reality bites and the justification no longer holds, as was considered to be the case here.
The second legal aside is the rather dubious argument put forward by the Commissioner of BIOT that the court had no jurisdiction to hear the case as the 2004 Order was made by the Crown “in right of the UK”, not “in right of BIOT”. If successful, only the UK courts would have jurisdiction to hear the case. This highlights the absurdity of Royal Prerogative legislation, as it requires the reader to ascertain which particular crown the monarch is wearing- their UK Crown, or their BIOT Crown, or perhaps their Crown as monarch of the single, undivided realm. For the Commissioner to succeed they would have to prove it was the UK Crown. This is notwithstanding that it is called the BIOT Constitution Order, published only in the BIOT Gazette and not anywhere in the UK, forming part of the law of BIOT, applying only in BIOT, enforceable in BIOT by the BIOT immigration officer. Thankfully, the judge dismissed this argument as “fanciful” [para 149].
Conclusion
In conclusion, the BIOT Constitution highlights the very worst of law-making using the Royal Prerogative. Although entitled “Constitution”, the only thing it does for its people is to exile them. It offends democratic norms as it was made by a UK Minister thousands of miles away, and not by the people affected by it. It undermines the rule of law as it is deliberately made inaccessible. The outcome was the exile of between 869 and 1500 Chagossians who now live scattered around the globe.
R v Mandarin has shone a light on the unjustified and archaic use of Royal Prerogative legislation. It is enough to repeat the actual text of the 2004 Order. It begins by stating that:
At Court at Buckingham Palace on 10 June 2004 …The Queen’s Most Excellent Majesty in Council… is pleased, by and with the advice of Her Privy Council, to order, and it is hereby ordered, as follows
Elizabeth II was pleased to order, in section 9, that her subjects, the Chagossians, had no lawful right of abode in the Chagos Islands.
Dr Ronan Cormacain, Consultant Legislative Counsel
My thanks to David Snoxell, Coordinator of the Chagos Islands APPG, Deputy Commissioner of BIOT (1995-97) and British High Commissioner to Mauritius (2000-04), and to Richard Dunne for their assistance with this paper. Any errors remain my own.
(Suggested citation: R. Cormacain, ‘Mandarin: Shining a light on prerogative legislation in the Chagos Islands’, U.K. Const. L. Blog (13th April 2026) (available at https://ukconstitutionallaw.org/))
UK Constitutional Law Association 