It was pointed out before the EU referendum that having a popular vote to defend parliamentary sovereignty was something of a quixotic exercise. Perhaps the fact that they majority of the public voted differently to the majority of MPs suggests that they were less worried about the parliamentary bit and quite happy to assert British popular sovereignty.
The implications of this are now beginning to play out. The Telegraph reports that Theresa May intends to give notice of Britain's intent to leave the EU, under Article 50 of the Lisbon Treaty, without further reference to Parliament. To my unpractised eye, withdrawal from a treaty looks like the kind of thing that normally falls within the royal prerogative. Yet there remains the question of whether the Government could take such an irreversible step out of the EU without Parliament having repealed the European Communities Act. Might that not be one of the domestic constitutional requirements alluded to in Article 50 itself?
There are real dangers for continuity remain MPs in taking a stand on parliamentary sovereignty, if that means directly challenging the popular mandate for Brexit. Given that there is little sign of any favourable shift in public opinion since the referendum, it risks a backlash that would entrench the Brexit majority and make any prospect of winning a different mandate in the future even more distant than it is now.
A much better strategy is to focus on the limits of that mandate. The Leave campaign during the referendum deliberately avoided putting forward a single policy model for Brexit, which in itself suggests that any given model might be less popular than Brexit itself. Some Brexit campaigners, such as Dan Hannan, argued for a Swiss or Norwegian model that included freedom of movement, something that was anathema to many others.
It will be that the latter group included the great majority of Brexit voters, but the majority of a majority is not necessary itself a majority. Parliament therefore has every right to hold the Government to account over the type of relationship with Europe that it seeks. In this respect, today's statement from Labour's Barry Gardiner hit just the right note:
“Those commentators who argue that the Prime Minister should circumvent a parliamentary vote and use the Royal Prerogative to leave the EU should consider what constitutional precedent they seek to invoke.
“The logic of saying the Prime Minister can trigger Article 50 without first setting out to parliament the terms and basis upon which her government seeks to negotiate; indeed without even indicating the red lines she will seek to protect, would be to diminish parliament and assume the arrogant powers of a Tudor monarch.
"Parliament cannot be side-lined from the greatest constitutional change our country has debated in forty years.”
This amounts to a call for Parliament to have a say over the process, not a veto over the Brexit mandate. It might seem flawed, in that the Brexit process can only start when Article 50 has been invoked, but Theresa May has effectively conceded the point by saying that she will not trigger article 50 until a UK approach and objectives have been established. Parliament is surely entitled to satisfy itself that this is the case.
In this situation, a Corbyn-led Labour Party would need to raise its parliamentary game. But Owen Smith's strategy of calling for a second popular vote may not be ideal either. Launching a frontal assault on the Brexit mandate may be helpful to him in the Labour leadership contest, but it provides ammunition to populist euro-scepticism without actually strengthening Parliament's hand. If as Smith says, there is a anti-Brexit majority in Parliament, then the aim should be to challenge not the principle but the concrete implementation of Brexit, and to stand up for all those constituencies which the Leave campaign said would not be harmed by Brexit (workers, farmers, current foreign residents, Scotland, Northern Ireland, etc).
If the Government's plan failed to stand up to that scrutiny, it might be the Brexit camp which would be forced to seek a new popular mandate on a much more concrete prospectus. Euro-sceptics would undoubtedly feel aggrieved by such an outcome, but it would be the product of their strategy in the first referendum. Right now, they would probably win that renewed mandate, but it is impossible to know what the political landscape will look like in 2020.
Whether this strategy is realistic depends ultimately on whether that notional pro-European majority in Parliament still exists in the face of the referendum outcome and the disappearance of Cameron-Osborne patronage.