Global menu

Our global pages


Supreme Court Judgment: UK Parliament must authorise Article 50 Brexit notice

  • United Kingdom
  • Brexit
  • Competition, EU and Trade - Brexit


On 24 January 2017, the UK Supreme Court handed down its judgment by a majority of eight to three that an Act of Parliament is required before the UK Government can give notice under Article 50 of the Treaty of European Union to leave the EU. This decision means that the UK Government will now need to consult UK Parliament and obtain its approval before notice can be given to the European Council to leave the EU. The key issues resulting from the majority judgment are:

  • The judgment makes no difference to the decision to withdraw from the EU.
  • The judgment says nothing about the UK’s future relationship with the EU.
  • Parliament decided to enact the European Communities Act 1972 (“ECA”) and to make a “partial transfer of law-making powers” to EU institutions, “unless and until Parliament decides otherwise”. The decision reinforces the sovereignty of Parliament in relation to the ECA and the UK’s membership of the EU. Withdrawal from the EU Treaties by the giving of the Article 50 notice is therefore a matter for Parliament.
  • Withdrawal from the EU by the giving of the Article 50 notice “makes a fundamental change to the UK’s constitutional arrangements by cutting off the source of EU law”. Fundamental changes to the constitution need parliamentary legislation. So a resolution of one or both Houses will not be enough.
  • EU law confers domestic rights on UK citizens. Removing these rights by repealing the ECA needs Parliamentary authority.
  • The Supreme Court found that very clear words, authorising Government to withdraw from the EU, would have been needed in the ECA for Government to have that power. There are no such clear words.
  • In relation to the devolution issues, the court was undivided in their view that relations with the EU and other foreign affairs matters are reserved to Government and Parliament.
  • This means that the devolved legislatures do not have a veto on the UK’s decision to withdraw from the EU.
  • In relation to Northern Ireland, the Judges opined that neither Section 1 nor Section 75 of the Northern Ireland Act 1998 (“NIA”) applied. The purpose of the NIA was to give the people of Northern Ireland the right to determine whether to remain part of the UK or to become a part of a united Ireland. It did not, in their opinion, regulate any other change in the constitutional status of Northern Ireland.
  • The Sewell Convention provides that the UK Parliament may not legislate for devolved matters without the consent of the devolved parliament. Withdrawal from the EU will change the competence of devolved institutions and will remove the responsibility to comply with EU law. However, the Judges concluded that the Sewell Convention is no more than a political convention between the UK and the devolved institutions, and although they recognised the importance of it, it remains as such. Accordingly, they concluded that the Sewell Convention does not give rise to a legally enforceable obligation but a political restriction on the activity of UK Parliament only, which they cannot rule upon.


The majority decision does not say anything about the deal that the government will conclude with the EU on exit. The key question is whether this majority judgment is likely to affect Theresa May’s timetable for Brexit as a result of full parliamentary involvement. In this regard, David Davis has stated that the Government will “within days introduce legislation to give the Government the legal power to trigger Article 50, and begin the formal process of withdrawal” from the European Union and that it “will work with colleagues in both Houses to ensure this Bill is passed in good time for [it] to invoke Article 50 by the end of March this year”. It remains to be seen how long the parliamentary process will take and what conditions, if any, may be attached to parliamentary approval.


Visit our Brexit Legal Advice Hub for in-house lawyers