In one of most important constitutional cases of modern times, the Supreme Court ruled by a majority of 8 to 3 that the prime minister cannot use royal prerogative to trigger Article 50 and start the UK’s two-year exit from the EU. (Supreme Court rules MPs must vote on triggering Brexit)

A supreme court ruling ensured that the MP's that don't belong to the devolved governments of Wales, Scotland and Northern Ireland would need to be legally consulted before invoking Article 50. What does it change in comparison to Theresa May using Royal Prerogative to invoke Article 50?

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    It makes the passage of leaving the EU, and what replaces it more uncertain. It is not known which of the amendments of Labour, Liberals and SNP are likely to be accepted by the Speaker. But the proposed amendment (of Labour) that there has to be a meaningful vote before Parliament accepts any new deal, it seems to me, could be quite significant, if some Conservatives support it.
    – WS2
    Jan 24, 2017 at 12:03
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    Having said that, I do not see much likelihood that Art 50 will not be triggered, nor that negotiations will commence. The most likely remaining impediment to Britain leaving the EU lies in EU law. The invocation of A50 is almost certainly revocable, and the two-year period capable of being extended. Even if it requires the agreement of all 27 member governments that may be possible, given it is in virtually all Europe's interests for Britain to remain a member. And no one knows how opinion will move as the effects of the low-value pound, and other detriments start to bite on the economy.
    – WS2
    Jan 24, 2017 at 17:12
  • @WS2: I doubt all of this - it's in the interest of EU27 to make the Brexit as painful as possible for the UK to set precedent for other countries thinking about an exit. Jan 25, 2017 at 8:31
  • @MartinSchröder Wait till the British boycott of German cars starts! The alternative to the EU is that everyone adopts the mentality of Trump. UK European enthusiasts need some support from the continent.
    – WS2
    Jan 25, 2017 at 10:06
  • MPs don't belong to the devolved governments. England has MPs (Members of Parliament) these MPs sit in parliament in Westminster. Northern Ireland has Members of the Legislative Assembly (MLAs) who sit in the Northern Ireland Assembly and can only vote on devolved issues. NI also has MPs who sit in Westminster - they do NOT get to vote on devolved issues as they do not sit in the NIA. The same is true for Scotland (Members of the Scottish Parliament (MSPs)) and MPs and Wales (Assembly Members (AMs)) and MPs. Apr 11, 2017 at 21:14

1 Answer 1


By using the Royal Prerogative May would have been able to unilaterally invoke Article 50 without the chance for other MPs to object. Without it the MPs can now force a block on the triggering of Article 50 by means of a vote in parliament. That means May may not be able to actually trigger Article 50 as promised.

This is a stark difference to the previous claims of May's government that Article 50 will definitely be triggered in a timely manner and there is no chance of it not being triggered.

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    It might be worth mentioning that the chance of the vote failing seems fairly small at the moment, so the main effect of the ruling seems to be constitutional, not practical.
    – phoog
    Jan 24, 2017 at 19:18
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    @phoog Yeah, that is true. Based on the current numbers Brexit is still very likely to occur... its just 99.9% instead of 100% Jan 24, 2017 at 19:28

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