Documents to download

EU treaty

This paper covers Parliament’s role in ratifying treaties up to 2017.  This paper is no longer being updated by the Library. See our new paper 9247 ‘How Parliament treats treaties’ – for the most up to date information on this topic.

The Government makes treaties…

The UK Government is responsible for negotiating, signing and ratifying the 30 or so international treaties involving the UK each year.

The starting point for treaty ratification in the UK is that the Government has the power to make international treaties under its prerogative powers. But this cannot automatically change domestic law or rights, and – as the Supreme Court recently ruled in the Miller case – it cannot make major changes to the UK’s constitutional arrangements without Parliamentary authority.

…but Parliament has a limited role

Parliament (and/or the devolved legislatures) is therefore involved if domestic law needs to be changed in order to implement a treaty – but this does not give Parliament the power to approve, reject or amend the treaty itself. It also now has the opportunity to say that a treaty should not be ratified, but it does not have to debate or vote on most treaties.

This is in contrast to some other countries, where parliaments are involved in treaty-making and may need to give their consent before ratification (often because treaties can automatically be part of domestic law that can be relied on in domestic courts).

The 2010 Act: new power for the Commons to block ratification

Part 2 of the Constitutional Reform and Governance Act 2010 requires the Government to lay before Parliament most treaties it wishes to ratify, along with an Explanatory Memorandum. This gave statutory form to part of a previous constitutional convention on parliamentary involvement with treaties (the Ponsonby Rule).

The 2010 Act also for the first time gave parliamentary disapproval of treaties statutory effect, and effectively gave the House of Commons a new power to block ratification. The process is this:

  • The Government may not ratify the treaty for 21 ‘sitting days’ (ie days when both Houses were sitting) after it was laid before Parliament.
  • If within those 21 sitting days either House resolves that the treaty should not be ratified, by agreeing a motion on the floor of the House, the Government must lay before Parliament a statement setting out its reasons for nevertheless wanting to ratify.
  • If the Commons resolves against ratification – regardless of whether the Lords did or not – a further 21 sitting day period is triggered from when the Government’s statement is laid. During this period the Government cannot ratify the treaty.
  • If the Commons again resolves against ratification during this period, the process is repeated. This can continue indefinitely, in effect giving the Commons the power to block ratification.

Neither House has yet resolved against ratification of a treaty under these provisions, and there are limited options for how they can do so.

Despite looking like a major change, the provisions of the 2010 Act have several exclusions and limitations.


Some types of treaty are excluded from the 2010 Act:

  • exceptional cases
  • Memorandums of Understanding, and treaties that do not require ratification
  • some EU Treaties which already require an Act of Parliament or even a referendum
  • ‘double taxation’ agreements which require an Order in Council

Devolved executives and legislatures

The devolved executives and legislatures have very limited involvement in treaties, even though they may be responsible for applying them.

Treaty-making remains the exclusive responsibility of the UK Government, but it has agreed to cooperate on treaty negotiation and implementation

No requirement for debates or votes

Although the 2010 Act puts on a statutory footing Parliament’s opportunity to scrutinise treaties, it does not require Parliament to scrutinise, debate or vote on them (and it rarely does so).

There have been some calls for a process that results in more debates and votes on treaties, perhaps involving the committees, but Parliament has so far been reluctant to set up new mechanisms for treaties.

This is in contrast to many other countries where parliamentary approval is required at least for certain defined categories of treaty. Even some other ‘dualist’ countries have incorporated some kind of parliamentary scrutiny of treaties, for example Australia which has a dedicated Joint Standing Committee on Treaties.

Parliament can only oppose (or tacitly accept) a treaty in full – it cannot amend treaties.

Parliament cannot amend treaties

There is no general requirement or mechanism for parliamentary scrutiny of (non-EU) treaties while the Government is negotiating them. So Parliament is not usually involved at the stage when changes could still be made to the text of a treaty.

This is fairly typical; the US is rare in allowing the Senate Committee on Foreign Relations to propose amendments to treaties.

There have been several proposals for parliamentary involvement before signature, to minimise disagreements when it comes to ratification, but there is also considerable opposition to such ideas.

However, Brexit has re-awakened the debate on how Parliament should be involved with treaties. Many of the proposed amendments to the European Union (Notification of Withdrawal) Bill concerned Parliament’s role in the negotiating process or approving the final agreement. Although none of them passed, the Government did agree to give Parliament a vote on a withdrawal agreement before it is signed. And the likelihood of subsequent treaties having a major effect domestically, for instance on trade, might reignite calls for more parliamentary scrutiny of treaties.

Further information

Image copyright

Press Association

Publication details

Documents to download

Related posts