Withdrawal from the European Union would mean a "fundamental alteration" in the constitution of the UK that requires an Act of Parliament to initiate, according to Scotland's Lord Advocate.

The submission is made in the written case for the Lord Advocate, James Wolffe QC, who has been given leave to intervene, on behalf of the Scottish Government, in the UK Government's appeal to the Supreme Court against the High Court ruling that Parliament must authorise the giving of the article 50 notice that begins the formal withdrawal process.

Pointing out that withdrawal would have a "significant impact" on the UK constitution, since EU membership is assumed in each of the devolution settlements, with EU law constraining legislative and executive competence and EU membership affecting devolved powers, Mr Wolffe supports the reasons given in the High Court's decision. He further submits that "It is a matter of constitutional principle that laws cannot be amended or repealed by an exercise of the royal prerogative alone" – a principle reflected in the Claim of Right of 1689 as well as article XVIII of the Treaty of Union.

Withdrawal would change the legislative competence of the Scottish Government and the executive and legislative competence of the Scottish Government; it would disapply or disable EU laws which currently apply in Scotland; and it woukld disapply or disable domestic laws which depend for their effect on membership of the EU. "These are not changes which can be lawfully effected by an exercise of the prerogative, without the authority of an Act of Parliament."

The Lord Advocate adds that in line with the Scotland Act 1998, changes to devolved competence would normally be achieved by Order in Council, approved by both Houses of Parliament and consented to by the Scottish Parliament. Accordingly notice of withdrawal activates the Sewel convention, now given statutory form in the Scotland Act 2016. 

He recognises that the courts could not decline to recognise an Act of the UK Parliament passed without the consent of the Scottish Parliament, but argues that "it would not involve an impermissible interference with Parliament" for the court to fulfil its proper function of identifying the constitutional requirements, as referred to in article 50, under which the UK may lawfully decide to withdraw from the EU.

Click here to view the full submission. The UK Government's written submissions can be found by clicking here.

  • On Friday the UK Supreme Court announced that Lawyers for Britain Ltd has also bneen given permission to file written submissions in the appeal, but that applications from 4A Law and New Europeans have been refused. The appeal hearing begins on 5 December.