UK-Mauritius Agreement on the Chagos Archipelago

Lord Houghton of Richmond Excerpts

Monday 30th June 2025 Lords Chamber

[Lord Houghton of Richmond (CB)]

My Lords, I echo the words of those who have said, and will no doubt go on to say, what a pleasure it was to be in the Chamber to bear witness to a most delightful maiden speech and an equally thoughtful valedictory one.

The treaty relating to the Chagos Islands and the potential transfer of the sovereignty of those islands to Mauritius has received much parliamentary scrutiny in committees over the past three months. That scrutiny has thrown up multiple issues that many people are justifiably passionate about—the plight of the Chagossians, the protection of the marine environment, and concern about a superficially bizarre treaty that will cost us a lot of money to surrender the benefits of sovereignty. My principal interest, however, is the one that I deem the overridingly important one: the role that Diego Garcia plays in our strategic relationship with the United States of America.

On a personal level, I am very familiar with the UK base on Diego Garcia. It was part of my overseas command responsibilities when I was Chief of Joint Operations. I have visited the base and know from my time as Chief of the Defence Staff the critical role it plays in exercising UK sovereignty and therefore justifying the UK’s position as part of the legal chain that authorises the forward deployed forces of the United States the freedoms they need to prosecute offensive operations. It is not an overstatement to say that our role as the sovereign power enabling the United States the freedoms it needs to use the base in accordance with international humanitarian law represents an enormous contribution to the defence element of the special relationship.

My primary concern, therefore, is to help ensure that the treaty, if ratified, represents the best way of preserving those freedoms. Superficially, I am reassured. After all, the treaty has been subject to detailed scrutiny by both the UK and US Governments and enjoys the support of our Five Eyes partners and many other interested parties—yet I have some lingering doubts that I at least want to place on the record. My doubts emanate from two concerns that relate to the relatively, though not entirely, novel forms of warfare. One is political warfare and the other is a form of legal warfare that most now simply refer to as lawfare.

Political warfare is best described as non-military efforts to coerce or intimidate a country or an individual into actions that benefit the perpetrator. The form of political warfare I envisage as relevant to this treaty are actions by a hostile power to coerce or intimidate key individuals in the international criminal justice system or individuals in key positions in relevant Governments. Lawfare refers to the strategic use of legal proceedings to achieve a political or military objective, effectively using the law as a weapon. A number of witnesses to the International Relations and Defence Committee proffered the view that the need to enter into this treaty in the first place was primarily prompted by successful lawfare, which culminated in the advisory opinion of the International Court of Justice that has been referred to already.

My worry therefore emanates from the concern that this treaty might, in the relatively near future, fall foul of future political and legal warfare acting in concert. In this context, I have two principal concerns. The first relates to the worry that the transfer of sovereignty of Diego Garcia to Mauritius will bring it under the provisions of the African nuclear weapons-free zone treaty, designed to keep the area free of nuclear-powered or armed submarines. Currently, Diego Garcia sits outside the treaty provisions, but is there not a significant danger that this exemption will come under legal scrutiny and challenge as soon as this treaty is ratified?

My second concern is perhaps more substantive. It relates to the issue of sovereign responsibility. To me, the treaty as currently drafted masks an incompatibility. It clearly states that on treaty ratification the sovereignty of the Chagos Islands passes to Mauritius. But it also implies that the administrative authority to agree the United States the freedom to operate the Diego Garcia base for military operations is retained by the United Kingdom.

My concern here, although I am not a lawyer, is that a country cannot abrogate, alienate or transfer its sovereign responsibilities under international humanitarian law. So, will not the prosecutors of lawfare simply start to exploit the view that international humanitarian law negates a bilateral agreement and that the UK is no longer the relevant administrative authority when it comes to agreeing military action by our principal ally? I sincerely hope that my concerns are either ill-judged or misplaced, but I would like the Minister to reassure the House that these concerns have been fully considered.

A final and completely unrelated concern, which my noble and gallant friend Lord Craig separately thought should be raised, although the risk may be small, is potentially the greatest existential threat to the Diego Garcia base, and it is not from hostile activity but from rising seawater, tsunamis or earthquake. The airfield at the base is barely a metre above sea level. Does the treaty allow for early termination in the event that natural causes render the base inoperable? A hundred years is a long time to be paying for something that cannot be used. The Minister’s assurance on this would be welcome.