Our Parliament has little influence over UK treaties – this urgently needs reform for the 21st century
May 2025: Protest against the Chagos deal outside the Royal Courts of Justice (ZUMA Press Inc / Alamy)
4 min read
The passage of the Chagos agreement and its implementing bill through Parliament has shone a light on the inadequacy of the UK’s treaty scrutiny process. It harks back to another era. The UK is an outlier internationally in giving Parliament so little influence over treaties – and this should change.
Treaty scrutiny is governed by part two of the Constitutional Reform and Governance Act 2010 (known as “Crag”) which codified the “Ponsonby Rule” from 1924. Crag allows each House 21 joint sitting days to decide whether it wishes to vote against the ratification of a treaty. There are several problems with this.
For complex or politically-significant treaties, 21 sitting days is nowhere near enough time. Proper scrutiny involves a committee having time to take evidence from experts and report to the House for a debate. Governments of both parties have accepted that more time is needed for certain trade deals – but only those formally classified as a “free trade agreement” – and has adapted Crag procedures accordingly.
Without justification, the government refuses to take the same approach for other important treaties that may have equally significant implications. The Chagos agreement is a good example. The government turned down a request to extend the scrutiny period, even though it recognised the high level of public and parliamentary interest in the treaty and there was no immediate urgency to ratify.
Not only is there insufficient time to scrutinise some vital treaties but Parliament does not have the power to block the ratification of a treaty under Crag. The Commons can, in theory, delay ratification indefinitely if it repeatedly votes against a treaty, but this power has never been exercised. This is unsurprising since the government controls the use of parliamentary time and has often refused time for treaty debates. This happened most recently with the Chagos Agreement but there are other examples such as the trade agreements with Australia, New Zealand and the CPTPP.
Treaty debates are more frequent in the Lords but a vote against a treaty can be overridden by a ministerial statement. In the lifetime of Crag, there has only been one vote against a treaty: when the Lords opposed ratification of the Rwanda Asylum Partnership Agreement until further guarantees had been put in place.
The weakness of the mother of all parliaments’ role is out of step with the vast majority of other countries. Evidence to a recent inquiry by the International Agreements Committee was that 148 countries have a constitutional requirement for parliamentary approval of some or all treaties. This is the case even where, like the UK, treaties are not automatically integrated into domestic law.
Parliament has repeatedly called for reform of the treaty scrutiny process, but this has fallen on deaf ears
Over the years, governments have invoked the need for legislative implementation of treaties as a reason to oppose change, but this is misconceived. The scrutiny of implementing legislation is no substitute for scrutiny of the treaty itself because the policy choices made in the treaty are locked in by the time Parliament gets to consider implementing measures. Moreover, many treaties require no legislation, or it is needed only for some aspects of a treaty, as in the case of the Diego Garcia Military Base and British Indian Ocean Territory Bill.
Parliament has repeatedly called for reform of the treaty scrutiny process, but this has fallen on deaf ears. Governments have refused to engage seriously with the arguments that have been made by multiple Commons and Lords committees. Most recently, the International Agreements Committee has called for a range of practical changes to improve the operation from a parliamentary perspective. These could be implemented easily with political will on the part of government.
However, more fundamental reform of Crag is needed in the longer term to ensure that treaty scrutiny processes are fit for the 21st century. This government should not be afraid start that debate.
Emily Thornberry is Labour MP for Islington South and Finsbury, and chair of the Foreign Affairs Committee. Lord Goldsmith KC is a Labour peer and chair of the International Agreements Committee
