Is whole Supreme Court Brexit case based on a red herring?

So the government's case that it has executive power to take us out of the EU - by triggering Article 50 and without formal approval by Parliament - is that it used the royal prerogative to take us into the EU more than 40 years ago.

It also argues that the European Communities Act, passed by Parliament at the time to give effect to our membership, did not narrow or restrict the use of the prerogative.

And more than that, the government's QC James Eadie sees the European Communities Act as no more than enabling legislation - or a conduit - that actually extended prerogative power to alter domestic law so that it corresponded to European law.

And, says Theresa May's silk, what the prerogative creates, viz our membership of the EU, the prerogative can also take away.

Obvs.

Except that the Supreme Court judges seem to believe that without the European Communities Act we would not have become formal members of the European club in the first place.

And if they persist with the view that joining the EU was a partnership or joint enterprise between executive and legislature, they will ultimately rule that the approval of lords and MPs is also the "sine qua non" of departure.

Or to put it another way: they have raised questions about whether in fact the government had the exclusive executive power to take us into the EU in the first place.

Here, however, is the elephant sitting in the corner of the unassuming Edwardian room housing this momentous case.

It is by no means clear that what the case is all about - that triggering Article 50 means we are actually leaving the EU - is actually true.

There are plenty of respected lawyers who believe that having given notice of an intention to leave the EU by triggering Article 50, the government would then have two years to either negotiate the terms of its departure or change its mind and serve a new notice of an intention to remain.

Funnily enough, neither Mrs May nor the other side in this legal battle is prepared to countenance that triggering Article 50 is almost a non-event, or a super soft and reversible exit.

But even if the appellants don't care whether the historic nature of triggering Article 50 is a convenient political fiction, the learned Supreme Court judges - who will wish to be seen as the impartial friends of the people - will have to take a view on whether the whole premise of this dispute is a huge red herring.