UK-Mauritius Agreement on the Chagos Archipelago

Lord Purvis of Tweed Excerpts

Monday 30th June 2025 Lords Chamber

[Lord Purvis of Tweed (LD)]

My Lords, I have a Motion in my name in the debate. I thank the Minister for the open way in which we have had discussions since the agreement was laid before Parliament and put on record my thanks to the noble Baroness, Lady Chapman, for her willingness to host briefings in the department. I commend the International Agreements Committee and the International Relations and Defence Committee of this House for their work and the extremely helpful findings and recommendations they have made. So far they have not been referred to, but we will doubtless hear more about them in the next contribution. I reiterate what I have said on many previous occasions: that the clerks, in particular of the International Agreements Committee, serve Parliament with distinction. They carry out a vital role for this House and for Parliament as a whole.

I look forward to the contributions from my noble friends Lady Ludford and Lord Alderdice, with the experience and perspective they bring, and thank my noble friends on the respective committees for their consideration. I too am looking forward to the maiden speech of the noble and learned Baroness, Lady Prentis of Banbury, and thank the noble Lord, Lord Boswell, for his many years of very distinguished service, in particular as chair of the House’s European Union Committee. I congratulate them both on securing the family handover with such elegant precision today. If the usual channels failed in one thing, they have succeeded in another for this debate.

I want to consider three main areas: first, the circumstances that led us to this debate; secondly, the treaty itself, the issues it raises and why there needs to be further consideration of some of them; and thirdly, what we as a House should do going forward, including why the Motion in my name has been tabled and should, I hope, be supported.

We are here today because of the decision by the previous Conservative Government on 3 November 2022 to

“begin negotiations on the exercise of sovereignty over the British Indian Ocean Territory … /Chagos Archipelago”.

That Statement by Foreign Secretary James Cleverly, repeated here by the noble Lord, Lord Goldsmith—the other one—specifically referred to

“taking into account relevant legal proceedings”

and the

“intention to secure an agreement on the basis of international law to resolve all outstanding issues, including those relating to the former inhabitants of the Chagos Archipelago”.—[Official Report, Commons, 3/11/22; col. 354WS.]

That Statement, which apparently is now “obscene”, “dangerous”, “self-harm” and “a surrender”, was made by the noble Lord Callanan’s Government. This was a major change of policy. If the Benches on my right are in any doubt about that, it was a change of policy because the position was, to quote from a Written Answer from the previous Government made on 20 April 2021:

“There are no current plans for discussions with the Government of Mauritius on the future of the Chagos Islands”.


In March 2022, just weeks before the policy change, the Government said:

“The UK has no doubt about its sovereignty over the British Indian Ocean Territory”,


and on Mauritius, that

“we do not recognise its claim. However, we stand by our commitment, first made in 1965, to cede sovereignty of the territory to Mauritius when it is no longer needed for defence purposes”.

So, since the Government—the Conservative Government—still needed it for defence purposes but made the decision in November that year to open negotiations to cede sovereignty, the change of policy was significant. The treaty is a consequence of now completing the previous Conservative Government’s policy. Some who agreed with it then disagree with it now, but that does not change the fact that the Conservatives made a major policy choice to cede sovereignty and to do it under the context of the International Court of Justice decisions.

This was also a major legal decision, as, up to the change of policy in 2022 to cede sovereignty, the Government relied on their previous argument that the 1965 agreement to separate the archipelago was held to be legally binding by the UN Convention on the Law of the Sea arbitral tribunal in 2015. This was therefore reversed, and the relevant legal proceedings referred to was the process of the ICJ, which had responded to the request by the United Nations General Assembly for a determination on the lawfulness of decolonisation and had reported its advisory opinion in 2019. We know that it was found in the opinion that decolonisation was not completed lawfully, and the General Assembly responded to the advisory opinion by adopting resolution 73/295 on 22 May 2019.

In this debate, some noble Lords may well delve deeper into previous history, and may challenge the ICJ opinion—which am sure all noble Lords have read fully. It gives a clear factual history, and some of it, I have to be frank, makes very uncomfortable reading. Others may opine on the ICJ mechanisms and the significance of the opinion and the associated General Assembly resolutions—it is their right to do so. But none of that will change the fact of the November 2022 decision of the Conservative Government.

So, we have established that the previous Government decided to recognise in principle the case for the exercise of sovereignty by Mauritius over the archipelago, and they pursued this over many rounds of discussions on the terms of bilateral relations going forward on how our defence and security interests would be maintained. We may hear in the debate that, after 11 attempts, there was no agreement. But that was not changing the view of the principle of ceding sovereignty; it was no agreement on the actual terms. There is a difference.

As we have settled that, we can now turn to the terms before considering the position we should take on them. The question is: does a deal with deficiencies negate the principle of Mauritian sovereignty? The answer is no, as James Cleverly’s Statement is recognised in principle internationally. The issues are the implications of it, its application and the protection of Chagossian rights under it.

One implication presented is whether this treaty raises questions on other overseas territories. The IAC addressed this in paragraph 26, saying that

“the Agreement would not have any direct read-across”.

Another implication is the question of whether this limits our security or defence. Questions have been raised so far in the debate. The committee concluded that none of the witnesses it heard contested the Government’s view that the treaty will not, for so long as it remains in force, materially change the ability of the UK and US to operate the base at Diego Garcia. We now know that the United States agrees.

Maintaining protection of marine biodiversity has also been raised. In 2010, the UK declared 640,000 square kilometres of marine protected area around the territory. It has some of the most biodiverse waters on the planet and I noted that the committee welcomed the Government’s assurance that they will work closely with the Mauritian Government to establish a well-resourced and patrolled marine protected area. The committee added:

“We consider it vital that an appropriate portion of the annual development grant funding is allocated towards projects to support the new MPA”.


I hope that the Government agree with that. The committee makes the case for more financial scrutiny, and I agree. It is worth, for colleagues on my right, putting on record, because the noble Lord, Lord Callanan, forgot to, that when he was a Minister, his department was the largest disburser of UK overseas aid to Mauritius—we thank him for his work. It is also the case that these financial provisions are of a larger scale, and it is necessary to have further clarity and details on this commitment.

The Government should have been, and should now be, more transparent, including on the basis for establishing the funds in Article 11, but a critical part now is the recognition and restoration of rights to the diverse Chagossian community. I note the 11 June call from the Human Rights Council for the agreement to be renegotiated because it does not respect the rights of the Chagossians. I also note that the committee’s conclusion was that the UK should not be bound by this, but feels that we should all acknowledge the years—in fact, the generations—during which the community has been denied rights, from forced removal in the 1970s to the denial of resettlement in the 2000s. We owe that community both an apology and restoration of rights.

As both communities noted in a round-table event held by the IRDC in December 2024, representatives from members of the community based in the UK and Mauritius expressed unanimous dissatisfaction with the consultation on the part of both the UK and the Mauritian Governments, and were frustrated by their exclusion from the negotiations. Paragraph 46 of the report concluded with a regrettable perception that, it said, had some basis in reality: that, over many years, the interests of the Chagossians had been subordinated to the national security interests of the UK and its allies. It went on to say that it agreed with some witnesses that more could have been done, including in relation to employment at the base, and that the agreement does not provide a clear route to the resettlement of Chagossians in the Chagos Archipelago. It called on the Government to engage with Mauritius to establish a programme of resettlement of the islands, including for members of the community currently based in the UK. Paragraph 49 called on the Government to clarify what oversight and accountability mechanisms would be put in place to ensure transparency and the equitable and effective allocation of funds. In particular, it sought clarification of how Chagossians would be consulted in the administration of the trust fund and whether those based in the UK will benefit. I agree with all of those points; indeed, I agree with the committee’s letter to the Foreign Secretary:

“More meaningful engagement would have helped rebuild trust and lend greater legitimacy to the final arrangements”.


My Motion, therefore, would require the Government to fulfil recommendations of the IRC and also the requests in points 4, 5, and 6 in the IRDC letter to the Foreign Secretary to enhance Chagossian engagement by establishing a formal consultation mechanism and meaningful inclusion in decision-making: and how resettlement “will” be provided for, not just “may” be provided for. It would address the request for transparency and accountability. I hope that both the Government and, indeed, the Conservative Opposition will support this Motion. If this is our last opportunity in this House to speak on this treaty, I hope that we can at least agree for further protections of the community to be outlined before the Government ratify.

We have therefore established that the previous Government agreed in principle to cede the exercise of sovereignty in a manner consistent with international law. We have also seen that there are areas where, under this Government, more information and scrutiny are needed on their terms for the conclusion of that ceding. The question now is how we proceed.

We heard plenty of fire and brimstone from the noble Lord, Lord Callanan, who seemed rather incensed. He sought to give the impression that all routes for the Conservatives to secure a debate in the House of Commons under CRaG had been exhausted, blaming the failure of the usual channels and the Government’s intransigence. That is not entirely true, because the Conservatives had two opportunities during this scrutiny period to secure time in the House of Commons; we know through the Library Note guidance on CRaG that if the Government do not provide time, it can be done in opposition time. Yes, there were coat-tails to hide behind when it came to the Government not providing time, but I am afraid that the noble Lord, Lord Callanan, must have had a meeting with his Commons colleagues when they said that this was not important enough to use their time during the scrutiny period in the House of Commons.

I think that we must all have sympathy with the noble Lord. I can imagine that he was not too happy when they said that it would be for the unelected House to take this up. Students of political history will know that this would have been an impossible course of action. The Conservatives would never use the unelected House to limit the prerogative power to make treaties and to refuse ratification. Do not take my word for it; take theirs. In the debate on the Rwanda treaty, we debated the Motion in the name of the noble and learned Lord, Lord Goldsmith, for conditions on ratification. The noble Lord, Lord Wolfson of Tredegar, whose contribution we look forward to later on, sought to give me and everybody else very respectful and lengthy legal advice as to why we definitely should not have a Motion to delay ratification of a treaty. I look forward to his altered legal advice later.

Winding that debate, the noble Lord, Lord Sharpe of Epsom, called the Motion from the noble and learned Lord, Lord Goldsmith, constitutionally “unnecessary and misguided”. Presumably, this far wider Motion by his colleague is necessary and well informed. Setting aside the amnesia epidemic sweeping the Benches on my right, and in all seriousness, I thank them for the announcement made on 3 June in this House by the noble Earl, Lord Minto, that a fatal Motion had been laid and that they would press it to a vote. I can only commend him and the noble Lord, Lord Callanan, on being brave. They have reversed generations of Conservative policy never to have fatal Motions in this House. They have reversed generations of policy not to seek to interfere with the prerogative powers, and this major constitutional moment today has not gone unnoticed.

We have an opportunity to restore some of the rights that have been denied a community, which we should all be ashamed of. We have the ability to honour a commitment given by James Cleverly in November 2022 that we would abide by international law and would cede sovereignty. We also have an opportunity to ensure that, at this stage, we do it right. We should therefore honour our commitments, ensure rights and provide clarity, and we hope that the Government can do this before ratification.

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[Lord Robathan (Con)]

My Lords, first, I join everybody else in congratulating both the noble and learned Baroness, Lady Prentis, and her kinsman—or father, whichever term she would rather have—on their speeches, because I think it is a great occasion. We shall miss the noble Lord, Lord Boswell, for whom I have even spoken, and he still spoke to me after I had spoken for him at his constituency.

I should say that I find this issue very depressing. We are seeing our country and our country’s interests being undermined by human rights lawyers. Obviously, we have the Prime Minister, the noble and learned Lord, Lord Hermer, and Philippe Sands. I think—somebody will correct me if I am wrong—they all served in the same Chambers at the Bar. I must say to the noble and learned Lord, Lord Goldsmith, for whom I have a very high regard—he was a very good chairman of the committee when I was on it—that to use Philippe Sands as an interviewee is slightly strange, since he was a paid counsel of the Mauritian Government. I think that is right—noble Lords can correct me if I am wrong—so it seems to me that he is slightly party pris.

We heard from the noble and gallant Lord, Lord Houghton, about lawfare, and I think that this really is lawfare. I will quote Sir Christopher Greenwood, who I do not know at all. He said, according to the International Agreements Committee report, that the consequence of not ratifying the agreement is that

“it completely undermines our position that we are a state that wishes to promote the rule of law in international affairs”.

I am sure that Christopher Greenwood is a quite excellent lawyer, but he had, of course, been with the court for a dozen years or so, which does sometimes make you slightly think in a particular way. Any court—the International Court of Justice is one—is actually the servant of the members of the court. I think I am right in saying that, of the 15 members, one was Somali, one was Russian and one was Chinese. Somebody can correct me if that is wrong.

I shall also share a quote, because I think it is rather important, about the security of the UK, which we heard about from my noble friend Lord Howell at some stage. Last week, we had the delayed report of the national security strategy issued by this Government. I think it was the Foreign Secretary who said that we want to make the UK

“a harder target for our enemies.”

He also said that we have to have

“clear-eyed view of how we engage with major powers such as China in order to protect our national security and promote our economic interests”.—[Official Report, Commons, 20/6/25; col. 975.]

If anybody is under any illusions about this, the report states:

“Instances of China’s espionage, interference in our democracy and the undermining of our economic security have increased in recent years. Our national security response will therefore continue to be threat-driven”.


I do not consider China an enemy, but it is certainly not an ally. We have to be open-eyed about this. For instance, we might consider the treaty that we had with China over Hong Kong and how well it has stuck to the details of that.

We heard the most extraordinary attack on the Conservative Government by the spokesman for the Liberal Democrats. I was sitting next to the noble Lord, Lord Cameron, not a moment ago; I quoted to him what the spokesman said, and he said that that was absolutely not the case. Let us not just tick through the details; let us talk to people such as the noble Lord, Lord Ahmad, who were there.

[Lord Purvis of Tweed (LD)]

I refer the noble Lord back to Hansard for the Statement from James Cleverly, and I am afraid that he should withdraw his comment that I was incorrect. I quoted the Written Ministerial Statement from the Foreign Secretary.

[Lord Robathan (Con)]

I heard the noble Lord; earlier, we heard the noble Lords, Lord Ahmad and Lord Cameron, say entirely different things.

On the marine protected area, environmental matters are extremely important to the whole world. Can the Minister tell us in summing up how Mauritius will protect the reefs? We do not have enough boats to do it, and what boats does it have?

Finally, on the treaty, I have mentioned the treaty on Hong Kong. How about international law in the case of the Budapest memorandum, where Russia agreed to respect the treaties with Ukraine? Treaties are marvellous, but not always held to by the people who sign them.

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[Lord Murray of Blidworth (Con)]

My Lords, it is always a pleasure to follow my noble friend Lord Mancroft. The issue of the need for and legal underpinning of the Chagos treaty has been the subject of numerous excellent monographs written by a team of authors led by Professor Ekins, professor of law and constitutional government at Oxford, and published by Policy Exchange. My noble friend Lord Robathan referred to the country as having been undermined by human rights lawyers; I can say to my noble friend, “Not all of them”—including, of course, both Professor Ekins and me.

It is clear to my mind that the risk of an adverse judgment and the real risk to the operation of the UK-US airfield at Diego Garcia are overplayed by those who favour this treaty. Mauritius cannot as a matter of international law secure a binding judgment before an international tribunal establishing that it is sovereign over the Chagos Islands, because the United Kingdom is not required to consent to this dispute being adjudicated by the International Court of Justice.

Accordingly, the Government explain their position by saying that they anticipate that another tribunal, specifically the International Tribunal for the Law of the Sea, which has no jurisdiction over questions of sovereignty over territory, will “presuppose” that the ICJ’s 2019 advisory opinion has settled that Mauritius is sovereign and will thus proceed to exercise its jurisdiction in relation to disputes about the law of the sea on the premise that Mauritius, rather than the UK, is sovereign. But there is not a word about sovereignty over the Chagos Islands in that advisory opinion of the ICJ. Moreover, the elements of the opinion that are adverse to the UK’s administration of the islands are, as advisory, not capable of binding the UK to change its position that it had uninterrupted sovereignty over the archipelago for more than 200 years. Hence, any such presupposition by the International Tribunal for the Law of the Sea will be erroneous in fact and law.

So, the fabled rules-based international order, lauded by the noble Lord, Lord Hannay, does not in fact require this treaty in the form that it is put before Parliament. I can greatly shorten my remarks by otherwise adopting the remarks we heard from the noble Lord, Lord Blencathra. I share his concerns regarding the obligations that he has set out. I also share the concerns in respect of the Treaty of Pelindaba, in relation to the positioning of nuclear weapons on African soil, raised by the noble and gallant Lord, Lord Houghton. The Government have thus far flippantly dismissed that concern without explaining why. Can the Minister set out in detail why Mauritius will not be in breach of its obligations under that treaty if there are nuclear weapons positioned in the Diego Garcia base?

The noble Lord, Lord Purvis of Tweed, became very excited and suggested that my noble friend Lord Callanan had tabled a fatal Motion. If only that were so—unfortunately, even if the House is minded to pass my noble friend’s Motion this evening, it would, pursuant to Section 20 of the CRAG Act 2010, merely require the Minister or another Minister of the Crown to make

“a statement indicating that the Minister is of the opinion that the treaty should nevertheless be ratified and explaining why”.

[Lord Purvis of Tweed (LD)]

The noble Lord is a stickler for accuracy. I quoted Hansard from 3 June when the noble Earl, Lord Minto, said that the Conservatives had tabled a fatal Motion.

[Lord Murray of Blidworth (Con)]

It is an interesting point as to whether my noble friend Lord Minto was correct—

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[Lord Wolfson of Tredegar (Con)]

My Lords, it is a pleasure to follow the noble Lord, Lord Kerr of Kinlochard, although he will appreciate that I take a very different position in responding to this interesting and important debate.

Before I turn to the more controversial points, let me start with a point on which there is unanimity. I welcome my noble and learned friend Lady Prentis of Banbury, who gave a truly magnificent maiden speech. As an Attorney-General, she was respected across the whole of the other place, and I am sure that her contributions here will be similarly listened to with great care across the whole of your Lordships’ House.

In my tradition, when we finish the annual reading of the Pentateuch with the end of Deuteronomy, we immediately start again with the first chapter of Genesis. In that spirit of linking a beginning and an ending, I also take this opportunity to mark the valedictory speech of her father, the noble Lord, Lord Boswell of Aynho. I am sure that, as the noble Lord leaves this House, it must be an especial pleasure to see his noble kinswoman—as I believe she is known—make the first of what I hope will be many contributions to our work.

This debate is required by statute before a treaty is ratified. Normally, with a treaty under the Constitutional Reform and Governance Act, we just have a debate. This is a different case. A treaty that cedes British sovereign territory to a foreign power cannot be ratified without an Act of Parliament. Professor Richard Ekins, in a Policy Exchange paper, has set out how every concession of British territory since 1890 has been enabled by primary legislation, the most recent example being the surrender of Hong Kong to China. In addition, since 1945, whenever a colony has achieved independence, either within or without the Commonwealth, primary legislation has been passed to renounce UK sovereignty under those territories. Indeed, FA Mann, a leading authority on foreign relations and the legally applicable principles, regarded this not just as a constitutional convention but as a legal principle.

In the Explanatory Memorandum, the Government appear to confirm that this is the position. Can the Minister inform us when this primary legislation will be brought before Parliament? Can we have a clear assurance that the treaty will not be ratified unless and until that legislation has received Royal Assent?

That is a problem with the Motion in the name of the noble Lord, Lord Purvis of Tweed, and why, in preference, I will support my noble friend Lord Callanan’s Motion. The former Motion states that the Government should not ratify the treaty until various matters have taken place, but the noble Lord has not included passing an Act to permit the cessation of British territory. I do not know whether it is now Liberal Democrat policy that a Government can give away sovereign territory without an Act of Parliament. It is a little odd. Those Benches are always so keen for Parliament to have a say before we even act in our own self-defence or support militarily our allies, but, apparently, they are keen now for Parliament to have no say before we cede sovereign territory.

In that respect, I regret the terms of Article 1 of the treaty, which states:

“Mauritius is sovereign over the Chagos Archipelago in its entirety, including Diego Garcia”.


That purports to accept that Mauritius is already the sovereign power. That is not the case in international law, as the UK has said repeatedly and consistently until this Government took office. It is also not the case in domestic law. Schedule 6 to the British Nationality Act 1981 includes the British Indian Ocean Territory as one of the British Overseas Territories—and that is also reflected elsewhere in the Act. All of that can be amended only by domestic legislation and an Act of Parliament. If the Act is not passed and the treaty is therefore not ratified, the effect in international law of the Government even agreeing a treaty in these terms will be to weaken our legal position over the Chagos Islands, even before the Bill has been laid before Parliament, which is to be regretted.

Why are we here at all? We are here because Mauritius has claimed sovereignty since 1981, despite decades of Mauritian Governments saying that they did not make any such claim. As we have heard, an ICJ advisory opinion in 2019 opined against the UK’s administration of the islands. The noble Lord, Lord Hannay of Chiswick, referred to that as a “ruling” in a rare, but perhaps Freudian, slip. I suggest that it is not a ruling at all; it did not, in terms, talk about the sovereignty of the islands at all. An advisory opinion is not a ruling, a judgment or a binding decision of any sort. The clue is in the name: it is an advisory opinion.

The United Kingdom would have to agree for the International Court of Justice to deliver a binding opinion or judgment. We would have to agree to submit the question of jurisdiction to the ICJ. We have not. I would hope that, even under this Government, we would not. Without that, there would be no binding ruling from the ICJ. While I recognise the political force of advisory opinions, we need to be clear-eyed about them: they are not binding.

We as a country have never accepted that we would always act in accordance with advisory opinions. Indeed, in 1996, an advisory opinion came within one vote of holding that the use of nuclear weapons would nearly always be illegal. Would we, if that vote had gone the other way, have unilaterally disarmed ourselves of all or most of our nuclear arsenal? Perhaps we would have done if this Government, with this Attorney-General advising them, were in charge; I just do not know.

The Government appear to accept that the advisory opinion is not binding, but they say, “Oh, ITLOS—the International Tribunal of the Law of the Sea—may assume that the advisory opinion is binding and that Mauritius is sovereign and exercise its own jurisdiction on that false premise”. But there are two problems with that: ITLOS has no jurisdiction to adjudicate a territorial dispute, nor can it properly take it that the question of sovereignty has been decided by an advisory opinion.

To respond to a point from the noble Lord, Lord McDonald of Salford, the advisory opinion is not binding—to use the noble Lord’s words—on ITLOS. An advisory opinion, as is made clear on the website of the ICJ itself, is not even binding on the particular agency which has asked for the advisory opinion, so it is certainly not binding on ITLOS. Secondly and relatedly, the United Kingdom should not accept that its sovereign rights can be taken away from it by one tribunal, ITLOS, misreading and misunderstanding the advisory opinion from the ICJ.

To pick up the point made by the noble Lord, Lord Kerr, ITLOS has no jurisdiction in relation to this dispute and we should not accept any ruling that takes for granted that the ICJ has established authoritatively that Mauritius is sovereign, first, because it has not and, secondly, because we would not give our consent to any such judicial determination. We should not, I suggest, give up our sovereign territory because of a fear that ITLOS might wrongly issue some order for some vague protective or provisional measures against us at some future, indeterminate date.

Of course I recognise that an advisory opinion gives the risk that future legal proceedings could be brought against us, but it is a terrible precedent, I suggest, for us to give up territory because we are worried that an international tribunal might in the future reach a conclusion which we regard as legally flawed. I have to say that, if British foreign policy is henceforth to be at the mercy of the vote of the United Nations General Assembly, then it really is game over.

The noble and learned Lord, Lord Goldsmith, referred to the—excellent, if I may say so—report from his committee, which I enjoyed reading. In that report, there is a reference to the fact that if we were to stand in the face of an advisory opinion by the ICJ, we would somehow be in the same position as Russia is in relation to the invasion of Ukraine. I hasten to add that that is not the view of the committee, but it was the view ascribed in its report to evidence it took from Professor Sands. The notion that standing on our legal rights in the face of a non-binding advisory opinion makes us like Russia invading Ukraine is less a piece of considered legal analysis and more a piece of advocacy. My late father used to say about one partisan newspaper that it was difficult to see where the news ended and the comment began. When reading Professor Sands’ evidence to the committee, it was very difficult to see where the analysis ended and the advocacy began.

[Lord Purvis of Tweed (LD)]

I am listening attentively to what the noble Lord is saying. If he has time, could he outline a little more of the background to the decision James Cleverly made in November 2022 to open negotiations on the exercise of sovereignty?

[Lord Wolfson of Tredegar (Con)]

I am going to deal with the legal issues affecting this because the Government are saying to us, “We have no choice: we have to sign this because we have legal risk”. There is no point the noble Lord muttering from a sedentary position.