UK-Mauritius Agreement on the Chagos Archipelago

Lord Goldsmith Excerpts

Monday 30th June 2025 Lords Chamber

[Lord Goldsmith (Lab)]

My Lords, the Motion standing in my name on the Order Paper invites the House to take note of the recent report of the International Agreements Committee, which I have the honour of chairing. I too look forward to the maiden speech of the noble and learned Baroness, Lady Prentis of Banbury, and to the valedictory address of my good friend, if I may say so, the noble Lord, Lord Boswell of Aynho.

The International Agreements Committee examined this agreement as thoroughly as time allowed. The noble Lord, Lord Callanan, in his opening observations, made the point that there are deficiencies in the Constitutional Reform and Governance Act. I agree with him on that; there are deficiencies. A review by my committee is in place at the moment to look at those deficiencies and, ultimately, to invite the House to help cure them.

One of those is the time that is allowed for the committee to consider the treaty, which is 21 sitting days. We asked the Foreign Office for an extension to the statutory 21 sitting days that we are allocated to scrutinise this agreement in view of the significant national interest involved. This request was denied without explanation. This raises an issue in relation to the operation of the Constitutional Reform and Governance Act. We will come back to that. To some extent, the time problem was mitigated by the International Relations and Defence Committee opening its own inquiry. By agreement, we co-operated in the holding of evidence sessions. I thank that committee, its chair, members and clerk for their co-operation. I also very much thank members of the International Agreements Committee, a number of whom are slated to speak today, for their co-operation, insights and wisdom.

I turn to our key takeaways. The House will know that the Chagos Archipelago is located in the middle of the Indian Ocean and consists of more than 1,000 small islands. On the largest of them, Diego Garcia, the UK operates with the United States a joint military base that is a vital strategic UK asset. When Mauritius was a colony of the United Kingdom, the islands were administered by the UK as part of Mauritius. They were separated from Mauritius prior to its independence in the mid-1960s. That separation is the crux of the legal dispute about sovereignty between Mauritius and the UK, which has been running for many years. As a direct result of the Mauritian campaign, the International Court of Justice gave an advisory opinion in 2019 which found that the UK’s assertion of sovereignty over the Chagos Islands was unlawful.

The agreement that we are considering intends to resolve the sovereignty dispute once and for all and secure the long-term future of the military base. Our report supports the contention of the Government that the agreement secures UK and US operations at the base at Diego Garcia, but the arrangements by which the UK is authorised to operate the base are time limited. Our committee also concluded that while the agreement is not perfect—I will speak to some of the limitations in a moment—if an agreement were not reached, Mauritius would likely resume its campaign to obtain a legally binding judgment on sovereignty against the United Kingdom.

We heard expert evidence from Sir Christopher Greenwood, one of the UK’s pre-eminent practitioners of international law and a former judge of the International Court of Justice, nominated by the United Kingdom to that court. In his opinion, any international court examining the sovereignty dispute would likely find in favour of Mauritius. Such an outcome would clearly represent a risk to the future of the military base and thus UK national interests and security.

I will briefly discuss the committee’s view on the justification for the agreement, taking into account the advisory opinion of the International Court of Justice in 2019. After this discussion, I will outline the report’s findings on the interests of the Chagossian people, rightly referred to by the noble Lord, Lord Purvis of Tweed, and others; the protection of the marine environment; and the financial arrangements under the treaty—all issues that have been raised and are touched on in the committee’s report.

First, on the Government’s justification for the agreement, particularly in view of the national security interests that the UK has in the base at Diego Garcia, Sir Christopher Greenwood told our committee that while the 2019 ICJ opinion was only advisory, it is

“a very authoritative guide to the legal position. In reality, it would be very difficult for any state just to ignore an almost unanimous opinion of the international court”.

The consequences of this ruling have already been seen in the rulings of international tribunals and the actions of international bodies. Members who have read our report will have noted the copy of the UN official world map on page 11, which shows the Chagos Islands as the territory of Mauritius. Similarly, a 2021 ruling of the International Tribunal for the Law of the Sea decided that, following the ICJ advisory opinion, it had jurisdiction to determine the maritime boundary between Mauritius and the Maldives on the basis that Mauritius was sovereign over the Chagos Archipelago. We heard evidence that there were legal avenues by which Mauritius would be able to bring a sovereignty dispute before an international tribunal. There is therefore a clear risk that Mauritius could succeed in obtaining a legally binding judgment on sovereignty against the United Kingdom.

The issue of whether the base on Diego Garcia is secure against litigation is an important one, given its centrality to the UK’s national security interests. I note the point about the possibility that it might even have been used last week in the US attacks on Iran. The base was described to us in evidence as a “vital” security asset. It sits at a strategic location in the centre of the Indian Ocean, which offers air cover into the Gulf, the Middle East, south Asia and east Africa, and thus protection for crucial shipping lanes in the region, among other security concerns.

Nothing in our inquiry—we looked hard at this point, in so far as we could—contradicted the Government’s view that the agreement would prevent the UK or US retaining full control over operations from Diego Garcia; nothing in the agreement would prevent that. The US Government have also welcomed the agreement, a further sign that it will not constrain activities at the base.

Our inquiry did consider the risk of China’s operations in the region and its relationship with Mauritius. Again, however, we did not hear of any credible threat to the stability of operations at the base that could come about as a result of the agreement. We do, however, note in our report that there is no guarantee that the agreement will be extended at the end of the 99-year term.

I turn to the interests of the Chagossian people, which we looked at. The past treatment of the Chagossian people has left a “deeply regrettable legacy”; that is acknowledged in the preamble to the agreement. However, the agreement makes minimal provisions to support Chagossians. It states simply:

“Mauritius will now be free to implement a programme of resettlement on the islands of the Chagos Archipelago, other than Diego Garcia”.


In fact, that does nothing to secure the right to return of the Chagossian community. At the December round-table event with members of the Chagossian community, our colleagues on the International Relations and Defence Committee heard unanimous concern that Chagossians had been excluded from the consultation process by the British and Mauritian Governments, and that any engagement had felt “tokenistic” and “superficial” and lacking in meaningful engagement or follow-up.

The omission from the agreement of meaningful consultation with and provision for the Chagossian community is regrettable. We note the perception, which we believe has basis in reality, that, over many years, the interests of the Chagossians have been subordinated to the national security interests of the UK. Our committee is of the view that more should have been done to secure the rights of Chagossians in this process; for example, by prioritising Chagossians for employment at the base on Diego Garcia. Our report therefore calls on the Government to engage with Mauritius to establish a programme of resettlement on the islands, including for members of the Chagossian community based in the UK.

I turn to another topic, which noble Lords have referred to, which is protection of the marine environment. We heard compelling evidence from Dr Bryan Wilson, the scientific adviser to the Chagos Conservation Trust and a research fellow in biology at the University of Oxford, about the importance and uniqueness of the marine environment around the Chagos Archipelago. He told us it is

“the most important reef wilderness on the planet”.

To date, the UK has been conserving and protecting this area with its own marine protected area. This is the first such marine protected area to change sovereignty. The UK experience has demonstrated that maintaining and enforcing a protected area of this size is challenging. Mauritius has an enormous task ahead of it. As such, our report welcomes the Government’s assurance that they will work closely with Mauritius to establish a well-protected marine environment, including by apportioning an appropriate amount from the annual development fund established under the agreement to support these activities.

That leads me to the financial terms. We have heard that the burden to the taxpayer of the financial payments under this agreement is high. These costs amount to a total of £3.4 billion over the lifespan of the agreement. In addition to the annual cost of leasing the base, the figure includes a one-off payment to capitalise a trust fund for the benefit of the Chagossian community, and an annual development fund to contribute to projects to support the welfare and development of the Mauritian people.

There is little detail in the agreement as to how these latter two funds will be administered or audited, or if there exist criteria for their allocation. Greater clarity on this is needed. Our report calls on the Government to clarify what oversight and accountability mechanisms will be put in place to ensure transparency and the equitable and effective allocation of those funds. In particular, we would like clarification on how Chagossians will be consulted in the administration of the trust fund, and we would further like to know whether Chagossians based in the UK would benefit from this fund.

The summary of our committee’s work is that we agree with the Government that securing the long-term use of the base on Diego Garcia is of the highest importance. I strongly suspect that that is the view of everybody in this House. We heard nothing to undermine the Government’s contention that this agreement achieves that goal, for as long as it remains in force.

Taking account of the agreement’s limitations, to which we draw attention, our report concludes that, if the agreement is not ratified and if a future Government attempted to go on resisting international pressure to transfer sovereignty over the Chagos Archipelago, there is a risk that Mauritius will obtain a legally binding judgment on sovereignty against the United Kingdom. In these circumstances, despite its imperfections, we considered that the agreement was the safest way to secure the UK’s operation of the base on Diego Garcia.

--- Later in debate ---

[Lord Goldsmith (Lab)]

Has the noble Lord considered the evidence given by Sir Christopher Greenwood, former judge at the International Court of Justice—in a sense, our former judge—who dealt with specifically that point, as well as other points that have been discussed?

[Lord Wolfson of Tredegar (Con)]

I have; I read absolutely what Sir Christopher said about Article 4, but it did not find his way into the final report.

[Lord Goldsmith (Lab)]

It did.

[Lord Wolfson of Tredegar (Con)]

Well, it touched on it.

[Lord Goldsmith (Lab)]

It is in the final report.

[Lord Wolfson of Tredegar (Con)]

The point I have made about Article 4 is absolutely right. Mauritius can take measures in response.

I will wrap up because of the time. My noble friend Lord Callanan reminded us of the price we will have to pay for this legal farrago. Thanks to the approach taken by the Attorney-General, whose advice, properly, cannot be disclosed, the ultimate position is that we are not just giving up the Chagos Islands to a country which never owned them and is thousands of miles away but are paying it handsomely for the privilege.

I do not know whether my friend, the Attorney-General, is thinking about doing his bit to get our sluggish economy going by deciding to move home and increase transactions by putting his property on the market, but if he does, I hope that he might allow me to enter negotiations with him about the ownership of his house. I suspect that the result might be that I end up as the owner of his house having used his own money to pay for it.

The truth is that this is a legally unnecessary and badly drafted treaty. It is a treaty with holes in, and which contains within it the seeds of further disputes. It is a treaty under which we are paying Mauritius to take our sovereign territory off our hands, and we are paying it very handsomely for that purpose. For those reasons, I urge the House to support the Motion in the name of my noble friend Lord Callanan.