The Supreme Court has confirmed that it will hear the UK Government's appeal of the High Court's decision on the triggering of Article 50 from Monday the 5th to Thursday the 8th of December.

The importance of the case is illustrated by the expedited timetable, the fact that a four-day hearing is not only two days longer than had been expected but also longer than the Supreme Court usually allows, and the Court's confirmation that all 11 judges will hear the case. However, the Court will not be rushing to judgment: a court spokesman advised that the decision would be issued "probably in the new year.

The other significant development in the case is that the Scottish Government has indicated that it intends to intervene in the Supreme Court proceedings. In order to do so it will have to ask the Court for permission to intervene in the public interest. This process will involve submitting an application setting out the grounds on which the intervention should be permitted, and in particular the issues the Scottish Government wishes to address.

The UK Government would have the opportunity to oppose the granting of permission, but whether it will do so remains to be seen. The usual process would then be for a panel of Supreme Court Justices to consider the application and any opposition on the papers (i.e. without an oral hearing). If permission is granted, the Scottish Government will be permitted to intervene in writing (usually subject to a word limit) or in writing and orally in the hearing (usually subject to a word limit and a time limit).

While the Scottish Government has indicated that it supports the High Court's decision, the Supreme Court expects interveners to do more than just reinforce arguments that the parties are capable of putting forward themselves. Given that the claimants' arguments have largely been framed from a public interest perspective it may not be easy to find a new line to take on those, but it seems unlikely that the Supreme Court would refuse the Scottish Government's application.

Sewel convention and the Scotland Act 2016

In any event, the Scottish Government's announcement of its intentions suggested that it may ask the Court to declare that the Scottish Parliament's consent should be sought to any Westminster legislation authorising the use of Article 50. As explained previously, there is a convention (generally known as the Sewel convention) that the UK Parliament will not legislate on devolved matters unless the Scottish Parliament consents to that. This convention was given statutory form by the Scotland Act 2016.

The usual mechanism for the Scottish Parliament to give its consent is through a legislative consent motion (LCM). Refusing to pass an LCM does not constitute a legal veto as Westminster retains the ability to pass any legislation it wants, but ignoring a refusal of consent could, of course, have significant political ramifications.

The Scottish Government's position is that an LCM would be needed for any legislation approving the use of Article 50, on the basis that triggering Article 50 would eventually result in EU law being disapplied in Scotland, including in devolved areas of law. The UK Government would no doubt counter that any legislation relating to Article 50 was principally concerned with foreign affairs and international relations, which are reserved matters outside the Scottish Parliament's legislative competence.

These issues could probably merit a day of argument in the Supreme Court by themselves, particularly given that there would also have to be a preliminary question of whether the Sewel convention is a matter on which the courts should have any role at all. When the Scotland Act 2016 was going through the House of Lords the UK Government stated that the statutory expression of the convention was not justiciable, but the point has not yet been tested (and several legally-distinguished Lords doubted the UK Government's position).

Whether the Supreme Court will be prepared to open up the case to consider that wider issue remains to be seen. It is open to the Supreme Court to grant a qualified permission to intervene that limits the issues the intervener may address, and the Court may take the view that the case already carries enough constitutional complexity and political controversy without adding a new layer of each. In that case it could limit any intervention to arguments on the core Article 50 point, without allowing further submissions on what should happen next in the event that legislation is required and proposed. Alternatively, the Court could take the view that in that scenario the issue would probably end up back before it anyway, so it may as well address it definitively at an early stage.

Given the compressed timetable for the appeal we are likely to know soon whether the Scottish Government will be permitted to take part, and (the more interesting question) what the extent of their participation will be.