Diego Garcia Military Base and British Indian Ocean Territory Bill — Select Committee report: 14th Report of the Constitution Committee

Ordered to be printed 19 November 2025 and published 20 November 2025
Published by the Authority of the House of Lords
HOUSE OF LORDS
Select Committee on the Constitution
14th Report of Session 2024–26
HL Paper 21 6
Diego Garcia
Military Base and
British Indian
Ocean Territory Bill

Select Committee on the Constitution
The Constitution Committee is appointed by the House of Lords in each session “to examine
the constitutional implications of public bills coming before the House and to keep under review
the operation of the constitution and the constitutional aspects of devolution”.
Membership
The Members of the Constitution Committee are:
Lord Anderson of Ipswich Lord Griffiths of Burry Port
Baroness Andrews Baroness Hamwee
Lord Beith Baroness Laing of Elderslie
Lord Bellamy Lord Murphy of Torfaen
Lord Burnett of Maldon Lord Strathclyde (Chair)
Lord Foulkes of Cumnock Lord Waldegrave of North Hill
Declaration of interests
Information about interests of Committee Members can be found in the last Appendix to this
report.
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Fourteenth Report
DIEGO GARCIA MILITARY BASE AND BRITISH INDIAN
OCEAN TERRITORY BILL
1. The Diego Garcia Military Base and British Indian Ocean Territory Bill was
introduced to the House of Lords on 21 October. Committee stage began on
18 November.
2. The Bill makes provision to implement the Agreement between the
Government of the Republic of Mauritius and the United Kingdom
Government concerning the Chagos Archipelago including Diego Garcia
(‘the Agreement’), signed on 22 May 2025. The Agreement provides for
a transfer of sovereignty to Mauritius, with the UK exercising rights on
Diego Garcia during an initial 99-year period, which can be extended by
agreement.
3. The Bill gives rise to two issues of constitutional significance. This
report draws these to the attention of the House.
Parliamentary scrutiny of treaties
4. On 22 May, the Agreement was laid before both Houses of Parliament, as
required by Part 2 of the Constitutional Reform and Governance Act 2010.
Under that Act both Houses have 21 sitting days in which to scrutinise
the Treaty—and to pass a resolution to oppose the Treaty’s ratification if
desired—before it can be ratified by the Government. Both the Foreign
Affairs Committee and the International Agreements Committee examined
the Agreement during this period. 1
5. The period of 21 sitting days ended without a resolution to oppose ratification
being passed, so the Government is now able to ratify the Agreement.
However, the Government has not yet done so, reflecting established
practice that a government will not ratify a treaty unless and until it is able to
implement that treaty in domestic law. This will be possible upon enactment
of the Bill.
6. Despite two early day motions being tabled, the Agreement was not debated
in the House of Commons.2 On 30 June 2025, the House of Lords debated
two motions together on the UK-Mauritius Agreement. The first motion,
tabled by Lord Callanan, Shadow Minister, called on the Government
not to ratify the Agreement and that motion was disagreed to on division.
The second motion, a standard take note motion from the International
Agreements Committee, was agreed to.3
7. The International Agreements Committee recently published a report, Treaty
Scrutiny in Westminster: Addressing the Accountability Gap, which makes the
case for reform of the treaty scrutiny process. It argues, among other things,
1 Foreign Affairs Committee, The Chagos Agreement , 23 June 2025, QQ 1–80 (Stephen Doughty
MP, Peter Candler); International Agreements Committee, UK-Mauritius Agreement on the Chagos
Archipelago including Diego Garcia (9th Report, Session 2024–25, HL Paper 146)
2 Early day motions carry no entitlement to a House of Commons debate or vote within the Constitutional
Reform and Governance Act 2010 scrutiny period.
3 HL Deb, 30 June 2025, cols 469–539

2 DIEGO GARCIA M ILITARY BASE AND B RITISH I NDIAN O CEAN T ERRITORY B ILL
that there is a “powerful case for specific legislative reforms, in particular to
provide for the parliamentary approval of significant treaties” and “a strong
case for legislating to address the time allotted for parliamentary scrutiny of
important treaties”.4
8. We draw the attention of the House to the International Agreements
Committee’s recent report on treaty scrutiny.
Orders in Council
9. Clause 5 provides a power both to implement the Agreement and to make
consequential provision in relation to the Act through Orders in Council,
which are a form of legislation made in the name of the Monarch “by and
with the advice and consent” of the Privy Council.
10. Orders in Council can either be statutory (issued under a ‘parent’ Act of
Parliament and usually involving parliamentary approval) or prerogative
(made on ministerial advice, without any statutory authority, by the Monarch
by virtue of the residual Crown power).
11. Orders in Council for the British Indian Ocean Territory, as is typical for
Overseas Territories, have historically been made by virtue of the prerogative.5
Clause 5 seeks to preserve the use of the prerogative to make Orders in
Council as a result of the Agreement.
12. Clause 5(4) provides that the new statutory power conferred by clause 5 does
not limit His Majesty’s powers under the prerogative, and clause 5(6) also
confirms that the future exercise of prerogative powers do not stem from
legislation. The Government states that subclauses (4) and (6) “together will
provide that the statutory power conferred by clause 5 does not limit any of
His Majesty’s powers under his prerogative”. It adds that “the intention is to
maintain a clear distinction between prerogative and statutory orders”.6
13. Clause 5 further provides that if the Orders in Council produced under
clause 5(1) amend, repeal or revoke any Act of Parliament or statutory
instrument, then they must be laid before Parliament as statutory orders and
will be subject to the negative procedure. In any other situation, the Orders
in Council are not subject to any parliamentary procedure. We note that this
is common in relation to Orders in Council made by way of the prerogative
power, particularly in relation to treaties, and that accordingly the powers
under clause 5 are exercisable with limited parliamentary scrutiny.
14. We draw this to the attention of the House as a matter of interest
during the passage of the Bill.

4 International Agreements Committee, Treaty Scrutiny in Westminster: Addressing the Accountability Gap
(10th Report, Session 2024–26, HL Paper 168), para 70
5 R (On the Application of Bancoult) v Secretary of State for Foreign and Commonwealth Affairs [2008]
UKHL 61
6 Explanatory Notes to the Diego Garcia Military Base and British Indian Ocean Territory Bill [Bill 285
(2024-25)-EN], para 32

3DIEGO GARCIA M ILITARY BASE AND B RITISH I NDIAN O CEAN T ERRITORY B ILL
APPENDIx : INTERESTS
Committee Members’ registered interests may be examined in the online Register
of Lords’ Interests at https://members.parliament.uk/members/lords/interests/
register-of-lords-interests. The Register may also be inspected in the Parliamentary
Archives.
For the Diego Garcia Military Base and British Indian Ocean Territory Bill report,
Members and Legal Advisers declared no interests.

4 DIEGO GARCIA M ILITARY BASE AND B RITISH I NDIAN O CEAN T ERRITORY B ILL