The High Court has now settled the matter, for the moment, and has issued it's judgement in what has been described as "the most important constitutional case". If that sounds like an exaggeration then the judges involved are the Lord Chief Justice, the Master of the Rolls and Lord Justice Sales, the two most senior judges in the High Court with the third member of the bench being one of the most experienced constitutional lawyers in the UK. They had the benefit of arguments from 10 QCs, including the Attorney General, and 13 junior counsel. The Scottish and Welsh Governments had counsel in attendance although neither, not surprisingly, took an active part. That context probably justifies it's description as "most important".
The High Court have decided that the UK Government does not have power to exercise the Crown prerogative power in order to give notice under Article 50 that the UK will leave the EU. Instead Parliament must be consulted following on from the fact it enacted the European Communities Act 1972 (and subsequent amendments) and because leaving the EU will affect domestic law and the rights of individuals in the UK and beyond. It is for Parliament to consider and agree any changes to domestic law.
The Court have set out a comprehensive, but readable, exposition of constitutional law around the sovereignty of Parliament and it's relationship with the prerogative of the Crown today, particularly with regard to treaties. The Court goes back to The Case of the Proclamations dealt with by Sir Edward Coke in 1610, through Dicey and his seminal work on the Law of the Constitution in 1915 and a raft of UK and EU cases familiar to any constitutional law student.
The outcome of their consideration is that they confirm the importance of the principle of the sovereignty of Parliament which has existed for hundreds of years. Parliament can make and unmake any law it chooses. A Government of the day cannot override the right of Parliament to make or unmake law by exercising the prerogative powers. To exercise the prerogative to give notice under Article 50 to the European Council would be a breach of the UK's "constitutional requirements" referred to in Article 50 if Parliament is not given a substantive chance to consider the changes which will be made to domestic law.
This is a unanimous and comprehensive decision of the High Court. It has clearly been carefully drafted, presumably with appeal in mind. None of the arguments put forward on behalf of the Government were accepted.
The recent decision of the High Court of Justice In Northern Ireland on Article 50 appears to be in conflict with this decision. However the Court in Northern Ireland was looking at a narrower constitutional point focussed on the provisions of the Good Friday Agreement and the Northern Ireland Act 1998. The Northern Irish court recognised that the High Court in London was addressing the overarching constitutional issues and chose not to stray in that direction. The High Court in London referred to the earlier Northern Irish decision and noted that they had not had the benefit of the extensive argument available to the High Court and were answering a different question from that before the High Court.
So where now? The Government have said that they intend to appeal the decision to the Supreme Court. Since it was clear whoever lost was going to appeal, the dates are probably already in the Justices' diary. They probably have a copy of the judgement in their bags for this evening! In any event, they promised to hear any appeal to allow the Government's timetable for triggering Article 50 by the end of March to proceed (if appropriate). If they uphold the High Court's judgement then this could have implications for the Government's Article 50 timetable, but that remains to be seen.
The politics of this potential delay are playing out already, with those in favour of Brexit calling "foul" and those in favour of remain welcoming the debate, a recognition of the role of Parliament and the time to consider further. The constitutional experts and bloggers are once again out in force as yet another twist in the Article 50 story emerges, a provision most of us had never heard of on the 22nd June 2016.