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Brexit: Article 50 - Supreme Court Judgment


The Supreme Court of the United Kingdom today ruled that the UK Government's proposal unilaterally to trigger Article 50 of the Lisbon Treaty without the express approval of the UK Parliament in parliamentary legislation would be unlawful as a matter of UK constitutional law.

As has been well publicised, triggering Article 50 starts the two year negotiation period leading to the UK's exit from the EU.

By a majority of eight to three (of the full eleven judge panel, sitting as a full panel for the first time), the Supreme Court upheld the November 2016 Divisional Court decision, as reported in our earlier briefing.

The full judgment can be found here, and a summary of the judgment here.

The main focus of the appeal was on whether the Government is entitled to rely on the royal prerogative power to make the Article 50 notification without a vote in Parliament. Arguments were heard on behalf of the appellant (the Government), the respondents (the two individuals who instigated the case) and various interested parties and interveners, including the devolved Scottish and Welsh governments. In relation to devolution it was argued that triggering Article 50 also required consultation with or consent from devolved bodies in Scotland, Wales and Northern Ireland.

The eight judges in the majority issued a joint judgment in which they found that an Act of Parliament is required to authorise ministers to make an Article 50 notification.

  • They identified a vital difference between (i) variations in UK law resulting from changes in EU law, which were brought into domestic law and sanctioned by Parliament through the conduit of the European Communities Act 1972 ("ECA"), and (ii) the fundamental change to the UK's constitutional arrangements, cutting off the source of EU law, that would inevitably result from Brexit. (It is worth noting that the parties had agreed that an Article 50 notification would be irrevocable.)

  • The majority rejected the Government's interpretation that the ECA's incorporation of EU law "from time to time" provided for under the EU Treaties was sufficiently flexible to accommodate the possibility of ministers withdrawing from the EU Treaties. In the absence of clear words in the ECA authorising ministers to withdraw from the EU Treaties (which Parliament could have incorporated), that fundamental change, as well as the removal of existing rights of UK residents that would follow from withdrawal from the EU, required parliamentary legislation as a matter of UK constitutional law.

On the devolution issues, in the light of the decision of the majority, the eleven judges unanimously found that the devolution Acts did not require the UK to remain a member of the EU: relations with the EU are reserved to the UK Government and Parliament. Further, the operation of the so-called Sewel Convention (whereby the UK Government will not normally legislate on devolved matters without the consent of the devolved legislatures) was not within the constitutional remit of the courts. Therefore, the devolved legislatures do not have a veto on the UK's decision to withdraw from the EU.

The Supreme Court is the final civil appeal court in the UK. Given that there were no EU-law specific issues raised by the parties potentially referable to the Court of Justice of the European Union, this ruling is the end of the road for the legal process on this issue. It paves the way for the Government promptly to table what is likely to be short-form legislation before Parliament seeking authority to trigger Article 50 by March 2017 (the Supreme Court expressly identified the form of such legislation as being a matter for Parliament). Whilst most commentators consider it unlikely that Parliament will ultimately block the triggering of Article 50, there are likely to be attempts to delay and/or to secure additional commitments from the Government on matters such as the UK's negotiating objectives and further parliamentary involvement in the Brexit process (notwithstanding the Government's recent commitment to give Parliament a vote on the eventual exit deal).

In the meantime, there are other Brexit-related legal challenges which will be determined in due course:

  • English High Court proceedings were recently launched as to whether withdrawal from the European Economic Area happens automatically on the UK's departure from the EU (as the Government and the EU Commission say it will) or requires approval from HM Treasury and an Act of Parliament.

  • Proceedings in the courts of the Republic of Ireland about whether a withdrawal notice under Article 50 can be revoked (which may ultimately be a matter for the Court of Justice of the European Union) and, as in the English proceedings, whether the UK can remain a member of the EEA despite its departure from the EU.
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