Today, the High Court has delivered the landmark ruling on the legal challenge to Article 50, and the Government has lost.   This is of great significance both constitutionally and politically, and could have wide-reaching ramifications for the timing of the UK’s exit from the EU.

Despite arguments by the Government that the making and unmaking of treaties is an established use of prerogative powers, the Court found that the Government does not have the power under the Crown’s prerogative to invoke Article 50. They said that it was clear that Parliament, through the European Communities Act 1972, intended to legislate so as to introduce EU law into domestic law, and therefore create rights in such a way that cannot be undone by exercise of prerogative power.  The judges also said that the “most fundamental” rule of the UK’s constitution is that Parliament is sovereign and can make and unmake any law it chooses.

The Government has said it is “disappointed” by the decision, and announced its intention to appeal, on the basis that it is determined to respect the result of the referendum. A certificate for the appeal to be ‘leapfrogged’ straight to the Supreme Court was granted by the High Court, and the Supreme Court is believed to be standing by to hear the appeal on the 7th and 8th  December. For the first time, it is also believed that all 11 Justices will hear the case. This heads off any criticism that a differently constituted court might have decided the case differently.

Whether the Government will win the appeal is very difficult to call. However, the High Court’s ruling was much more hard-hitting against the Government than many expected. It was made clear that they had lost the case before the judges even considered the claimants’ arguments, and that the judges were firmly on the side of Parliamentary control over executive power, following “strong constitutional tradition”. It is also difficult to see how the Government will be able to plug the holes in their argument about the effective loss of fundamental rights resulting from the enactment of Article 50.

For now, Theresa May is unable to lawfully invoke Article 50. She will have to wait until the appeal is heard, and in the event that the Government loses the appeal, there may need to be an Act of Parliament, voted on by both Houses. This presents a whole host of problems for the Prime Minister.

If the PM finds out in January, after an appeal, that she does need to pass an Act of Parliament to invoke Article 50, she may well be pressed for time to reach her own deadline of March 2017. While MPs are unlikely to vote down Article 50, as they will not want to be seen to be denying the will of the voters, they would have increased bargaining power with the Government to scrutinize the Brexit negotiating strategy.  There is the possibility that MPs might seek to amend the legislation and add conditions on Brexit, which could significantly delay the Bill’s passage through Parliament.  There are also the Lords to consider: a significant proportion have repeatedly threatened to block Brexit if they have the chance; and unlike MPs, Peers don’t have to worry so much about what those pesky voters think. While it may prove difficult for them to block Brexit, they could significantly delay the UK’s exit.

The result is also very difficult for Theresa May as Prime Minister. She now faces increasing pressure to meet her own deadline of triggering Article 50 by March 2017 or risks further embarrassment, and she has a number of potentially difficult backbenchers who have made it clear that they are willing to rebel. The majority of MPs were for remaining in the EU, and Theresa May’s governing majority is extremely slim.  She may therefore be forced to call a snap general election, to increase her majority and win a new mandate. However this will ultimately be determined by what the Prime Minister really wants: perhaps it suits her purposes better to stick with Parliament as currently constituted in order to stifle those in her own party who are pushing most stringently for a ‘hard’ Brexit.

One thing is clear: the decision made by the High Court has certainly thrown a spanner in the works for Theresa May and her new Government.