As widely expected, the UK Government has lost its appeal to the UK's highest court in the case of R (on the application of Miller and Dos Santos) v Secretary of State for Exiting the European Union and associated references.

The Supreme Court delivered its judgement at just after 0930 am GMT this morning. To recap, Article 50 provides that a country wishing to leave the EU must give a notice in accordance with its own constitutional requirements. The Court was at pains to point out that the issue had nothing to do with whether or not the UK should leave the EU but that the main issue before the Court was whether the Government could use its prerogative powers to trigger Article 50.

By a majority of 8 to 3, the Supreme Court ruled that the UK Government cannot trigger Article 50 without an Act of parliament authorizing it to do so, and to proceed otherwise would be a breach of constitutional law and principles stretching back many centuries. Section 2 of the European Communities Act 1972 provides that whenever EU institutions make new laws, those new laws become part of UK law, making them an independent source of UK law until parliament decides otherwise. Thus the Government cannot trigger Article 50 without parliament's say. Lord Neuberger, when giving the ruling, said that as UK domestic law would change as a consequence of ceasing to be part of the EU treaties, the rights of UK residents would also be affected.

Reactions to the Judgment

Speaking outside the Supreme Court earlier today, Gina Miller, the London-based investment manager and philanthropist who acted as lead claimant in the case against the Government, welcomed the ruling, saying "only parliament can grant rights to the British people and only parliament can take them away…only parliament is sovereign." Attorney General Jeremy Wright said the Government would "comply with the judgement of the Court and do all that is necessary to implement it".

What happens next?

The Government must therefore put a bill before parliament for approval. The issue facing the Government is that whilst both the House of Commons and the House of Lords are not expected to try to delay the bill's passage into law, there is clear divergence on what such a bill should say.

In anticipation of the decision, the Government is said to have prepared the necessary draft legislation already, and it is expected that a very concise bill, perhaps only a few sentences, will be presented to parliament as early as tomorrow, in the hope that it will become law in time for the Prime Minister to invoke Article 50 by the end of March. Both the House of Commons and the House of Lords will have to vote in favour-disgruntled members of parliament belonging to the Scottish National, Labour and Liberal Democrat parties, plus some Conservative MPs, are likely to seek substantial amendments to the bill.

"All this said, the chances of Brexit being blocked are slim to say the least. The Conservative party has a working majority of 15 in the House of the Commons, and a majority of Labour MPs have already stated that they will not stand in the way, with many likely to actually vote for Article 50."

-Tim Wright, Pillsbury

What about the devolved administrations?

On the secondary issues relating to devolution, in particular whether the Northern Ireland Act 1988 and associated agreements require primary legislation and consent of the Northern Ireland Assembly and/or people of the Northern Ireland, before the Article 50 notice can be served, the Supreme Court was unanimous in its judgement that the devolved administrations had no right to be consulted and could not veto Article 50.

Again perhaps not unexpected, this will come as a blow to the devolved legislatures (Northern Ireland, Scotland and Wales). Although the Government has previously said Scotland, Wales and Northern Ireland will be kept fully involved, the decision may further trigger nationalistic tendencies, perhaps bringing the breakup of the United Kingdom a step closer.