In a widely expected ruling, the Supreme Court ruled that the Government cannot trigger Article 50 without Parliament’s consent. I won’t go over the ruling in detail, as I’ve already discussed it here and here. Suffice it to say, I think the Supreme Court made the right choice. Ministers cannot use the royal prerogative to alter domestic law. To do so would fly in the face of centuries of British jurisprudence.
The court was also right to reject the notion that the devolved governments can veto Brexit. Foreign affairs are reserved to the British government, and the devolved legislatures have not been asked to consent to Westminster legislation that alters the competencies of EU institutions, even when it would affect devolved matters. Besides, the practice of seeking the consent of the devolved legislatures before Westminster legislates on matters within their competency is a political convention, not a legal convention. It does not abridge the supremacy of the Westminster Parliament. As Lord Neuberger of Abbotsbury observed at paragraph 145 of the majority judgment:
While the UK government and the devolved executives have agreed the mechanisms for implementing the convention in the Memorandum of Understanding, the convention operates as a political restriction on the activity of the UK Parliament. Article 9 of the Bill of Rights, which provides that “Proceedings in Parliament ought not to be impeached or questioned in any Court or Place out of Parliament”, provides a further reason why the courts cannot adjudicate on the operation of this convention.
Of course, as a matter of comity, the British government might wish to secure the consent of the devolved legislatures, but it is not legally necessary. That being said, if the British government acts without their consent, they must be prepared to accept the consequences of that decision.
Now, all eyes will be on Parliament. The Government has promised a short Brexit bill later this week, and they hope to take it through the Commons within the space of a fortnight. There has been talk that Labour and the SNP will try to amend the bill to ensure barrier-free access to the single market (among other things), but their chances of succeeding seem slim. They would need the support of every MP who isn’t a Conservative, along with 13 defections from the Government benches.
The House of Lords will be more of a wildcard since the Government doesn’t have a majority there. But while it will be easier for peers to amend the bill, the Government can always have the Commons reject their amendments during ‘ping pong.’ That would force the Lords to either insist on their amendment (and potentially scupper the whole bill) or give way. Historically, the Lords usually give way when faced with opposition from the Commons, and I suspect that will be the case here as well.