The Sewel convention is a constitutional principle that governs the relationship between the UK parliament at Westminster and the devolved legislatures in Scotland, Wales, and Northern Ireland.

The convention states that the UK parliament will “not normally” legislate on a matter that is devolved without first seeking the consent of the relevant devolved legislature. It is a self-denying ordinance by Westminster, designed to respect the autonomy of the devolved institutions.

The convention is named after Lord Sewel, the minister who first articulated the principle during the passage of the Scotland Act 1998. Sewel was the Scotland Office minister responsible for the progress of the Scotland Bill, which established the Scottish parliament, through the upper chamber in 1998.

In a debate in the House of Lords in July 1998, Sewel stated that while the devolution of legislative competence did not affect the ability of the UK parliament to legislate for Scotland, “we would expect a convention to be established that Westminster would not normally legislate with regard to devolved matters in Scotland without the consent of the Scottish parliament.”

The convention is still seen as a cornerstone of the UK’s devolution settlement. However, its interpretation and application have become a source of political and constitutional friction, especially since the 2016 referendum on Britain’s membership of the European Union (EU).

How the convention works

The UK government is expected to consult with the devolved administrations if it plans to introduce a bill with provisions that fall within the scope of the Sewel convention.

This approval is sought through a legislative consent motion (LCM). The devolved government will introduce an LCM in its legislature, which is then debated and voted on by its members (MSPs in Scotland, MSs in Wales, MLAs in Northern Ireland).

If the motion is passed, consent is granted. If it is voted down, consent is withheld.

Due to this reason the convention has sometimes been cited as a restriction on the sovereignty of the UK parliament.

Legal status of the Sewel convention

The Sewel convention was given statutory recognition in the Scotland Act 2016 and the Wales Act 2017.

The Scotland Act 2016 amended the Scotland Act 1998 to contain an explicit and specific legal reference to the so-called Sewel convention. Subsections (7) and (8) of section 28 in the Scotland Act 1998 now state:

“(7) This section does not affect the power of the Parliament of the United Kingdom to make laws for Scotland.

“(8) But it is recognised that the Parliament of the United Kingdom will not normally legislate with regard to devolved matters without the consent of the Scottish Parliament.”

The Wales Act 2017 contains this same language.

However, despite this statutory footing, the supreme court ruled in the famous 2017 Miller I case that the convention remains a political rule and is not legally enforceable by the courts. The court ruled that the Sewel convention did not require the consent of the devolved institutions for the government to notify the Council of the European Union of the UK’s intention to withdraw from the EU (triggering Article 50 of the Treaty on European Union).

The ruling found that the Sewel convention “operates as a political constraint on the activity of the UK parliament” and “therefore plays an important role in the operation of the UK constitution.”

It added: “But the policing of its scope and operation is not within the constitutional remit of the courts. The devolved legislatures do not have a veto on the UK’s decision to withdraw from the EU.”

This confirmed that, in legal terms, the UK parliament remains sovereign and can pass laws for any part of the UK, with or without consent.

The convention’s power, therefore, is said to lie in the political pressure applied by the longstanding convention, not legal force.

Between 2018 and 2023, the Westminster parliament passed six acts (five of which related to Brexit) where the UK government accepted that the Sewel convention was engaged but consent was refused by one or more of the devolved legislatures.

The Senedd’s legislation, justice and constitution committee observed in a 2021 report, following Brexit the UK and devolved governments came to “interpret the Sewel convention differently”.

The committee added: “It is critical that all parties find a shared understanding on the application of the Sewel convention to which all executive and legislative arms of the UK can agree.

“Failure to reach such an understanding, or to reform the Sewel convention, will render it obsolete and of little practical value, while at the same time building unnecessary friction between the governments of the UK.”

The Sewel convention and the EU (Withdrawal) Act 2018

The passage of the European Union (Withdrawal) Act 2018 represented a significant test of the Sewel convention.

The legislation, designed to provide a legal framework for the UK’s exit from the European Union, triggered a protracted dispute over the boundaries of devolved authority. It turned existing EU law into domestic UK law, creating “retained EU law”.

The key source of the friction was clause 11 of the original bill. This clause referred to the fate of powers in “devolved areas” – such as agriculture, fisheries, and environmental protection – that were returning to the UK from Brussels.

These areas were technically within the remit of the devolved legislatures. However, the UK government proposed to retain control over them temporarily to ensure a “UK-wide internal market.”

Both the Scottish and Welsh governments initially opposed this, characterising the move as a “power grab”.

On 15 May 2018, the Scottish parliament debated the legislative consent motion. It voted to withhold consent by a margin of 93 votes to 30.

During the debate, the minister for UK negotiations on Scotland’s place in Europe, Michael Russell, told the chamber: “If the motion is passed today, that will be the will of this parliament. What cannot happen… is what the UK government seems to want to happen.

“They want to ignore the reality of devolution. They want to drown out what this parliament says. But, not even they can pretend that no motion has been passed.”

In Wales, following a series of concessions and amendments from the UK government, the Welsh Senedd voted to grant consent. The concessions came in the form of an intergovernmental agreement.

In a statement on 14 June, the secretary of state for Scotland, David Mundell, delivered a commons statement in the commons on the application of the Sewel convention. Mundell argued that the UK government has followed the “spirit and letter of the devolution settlement at every stage.”

He added: “The bill is about ensuring that the whole of the United Kingdom has a functioning statute book on exit day, and about providing legal certainty for businesses and individuals throughout the country.”

Turning to the convention, Mundell maintained: “These are not normal times.”

He added: “We are now therefore faced with the reality that the Scottish parliament has not given consent for this critically important legislation that provides certainty across the UK. That is not a situation that any of us would have chosen. It is not, however, a crisis, nor is it unforeseen.

“While the devolution settlements did not predict EU exit, they did explicitly provide that in situations of disagreement the UK parliament may be required to legislate without the consent of devolved legislatures.”

The UK government thereby stated its intention to override the explicitly stated will of the Scottish parliament.

The EU (Withdrawal) Act received royal assent on 26 June 2018.

This marked the first time Westminster had legislated without the consent of the Scottish parliament after having recognised that a bill fell within the scope of the Sewel convention.

In January 2020, for the first time, all three devolved legislatures denied consent for the EU (Withdrawal Agreement) Bill. The withdrawal agreement was the result of the Brexit negotiations during Boris Johnson’s tenure as prime minister.

Defending the UK government’s decision to proceed, the then chancellor of the Duchy of Lancaster, Michael Gove, said the decision had not been “taken lightly.”

He added: “However, it is in line with the Sewel convention… The Sewel convention – to which the government remain committed – states that the UK parliament ‘will not normally legislate with regard to devolved matters without the consent’ of the relevant devolved legislatures.

“The circumstances of our departure from the EU, following the 2016 referendum, are not normal; they are unique.”

Additional resources

• House of Commons Library – Sewel Convention: https://researchbriefings.files.parliament.uk/documents/SN02084/SN02084.pdf