Today was the final day of the Supreme Court hearing of the Article 50 case (R (Miller and Ors) v Secretary of State for Exiting the European Union). The Court heard submissions from the Scottish and Welsh governments as well as the various interested parties in the case, as well as the Government's response to the arguments made against it since Tuesday.
The two sides' respective arguments are now well known. Both claim to be advocating the basic constitutional orthodoxy and dismiss their opposition's case as a radical departure from convention with serious and controversial consequences. Both claim that only their case articulates and respects the true sovereign will of Parliament.
What is striking, after four long days of technical legal submissions and counter-submissions, is just how different the parties' interpretations of the constitution are. It is still fair to say, as Mr Eadie QC noted in the High Court, that they are like "two ships passing in the night".
The nub of the case appears to be this: is EU law a part of the "law of the land", untouchable by the Government's prerogative powers, or a body of international law given domestic legal effect for the time being only?
The Government maintains that it can exercise the prerogative to trigger Article 50 because, even though this will affect (and potentially extinguish) the EU law rights of UK citizens, it is not changing the law of the UK, but rather an act on the international plane of the very sort that gave rise to those EU law rights in the first place.
The Respondents, by contrast, argue that those EU law rights have not merely been given effect by Parliament through the "conduit" of the ECA 1972 but have been created in domestic law by Parliament. Therefore the relevant question is whether Parliament has authorised the Government to trigger "the loss of statutory rights" that would arise from serving the Article 50 notice. If the rights have been granted by Parliament, they can only be taken away by Parliament: to conclude otherwise would be to "[turn] the doctrine of parliamentary sovereignty on its head".
Ultimately, this is the choice facing the Supreme Court. Both sides accept that the prerogative allows the Government to act without Parliamentary authority on the international plane. Both also accept that only Parliament can change the "law of the land". At the heart of the dispute is a question that reflects in microcosm the political debate that has led the UK to this point: has EU law ever truly become a part of the law of this land?
Read today's transcript here.