[The following was commissioned by Counsel Magazine and is also published here.]

I’ll take some things as read.

You’ll know there’s a legal challenge to the Government’s position that it is for it and not Parliament to decide what action to take following the result of the Referendum. And that the challenge will be heard in the Divisional Court in October with a likely leapfrog appeal to the Supreme Court in December.

You’ll be aware that the challenge raises a question about the nature of the limits to the Royal Prerogative. Will triggering Article 50 denude the European Communities Act 1972 of content? Will it deprive UK nationals of their rights as an EU citizen? Is it Theresa May’s finger on the trigger? Or is must it be by Act of Parliament?

Published alongside this piece is another arguing that these are political questions – and that the courts should not get involved. I disagree. That there are political ramifications to the answers doesn’t change the nature of the questions from legal.

Few of us would baulk at the suggestion that the courts have an important role to play in regulating the relationship between the citizen and the Executive. Or in circumscribing when the Royal Prerogative can and cannot be used. Baulkers, if there are any, should read the words of Lord Oliver in Rayner (Mincing Lane) v DTI [1990] 2 AC 418, 462:

as a matter of the constitutional law of the United Kingdom… the Royal Prerogative, whilst it embraces the making of treaties, does not extend to altering the law or conferring rights upon individuals or depriving individuals of rights which they enjoy in domestic law without the intervention of Parliament.

Indeed, publicly at least, even the Government says that the challenge raises a justiciable question. I can’t tell you what the Government’s pleaded position is because, remarkably, the Divisional Court has ordered that all documents produced by the Government be kept confidential.

But, as far as we are aware, the issue is not a live one. So let me turn to the question why the proper functioning of democracy requires that Parliament decide. There are at least four overlapping reasons.

First, Parliament is supreme. It chose to enact a referendum that doesn’t mandate our departure from the European Union. It chose one that the then Foreign Secretary recognised in Parliament as merely “advisory”. Mr Hammond went on to say that the Government would regard itself as bound by the result – but that political commitment does not alter the legal character of the European Union Referendum Act 2015 as advisory. To treat it as binding is to undermine the Supremacy of Parliament. It is to replace its intention, as enacted in the Referendum, with the intention of the Executive.

Second, the United Kingdom’s membership of the European Union gives us rights as individuals: to live abroad, healthcare cover on temporary travels, to accrue pension rights working in other Member States, and so on. Parliament has not acted to modify or abrogate those rights. It cannot be right that the Executive can. To say this is to do no more than articulate a specific instance of an important general rule about the limits of Prerogative Power. To ignore it is to put citizens at the mercy of the Government.

Third, the fact that it is advisory inevitably gives rise to the question: who does it advise?

We know Theresa May opposes a second vote on the outcome of our negotiations with our EU partners. We also know that others in the Conservative Party feel differently. Nicky Morgan, who as Education Secretary also publicly contemplated standing for the leadership, says that Parliament must have a say on the final deal. There are wide open spaces between these two positions. One will lead to us leaving the EU: Brexit, after all, means Brexit. The other might not. The difference between them reflects the personal approaches of those two politicians to the outcome of the Referendum. But the electorate has had no chance to speak on which position should prevail. The only choice was one made by Conservative MPs pursuing considerations which included (and I mean no criticism when I say this) parochial ones. To deny Parliament any say on the choice between these positions cannot be right.

Finally, alongside the question, ‘who did the referendum advise’ is the related one, ‘what did it advise’? The binary formulation put to the electorate “Should the United Kingdom remain a member of the European Union or leave the European Union?” skates over the many parallel universes offered up during the campaign: lower and not lower immigration, inside and not inside the single market, money spent and not spent on the NHS, retained and not retained regional investment and agricultural subsidies, and so on. These, and the trade-offs between them, are profoundly important questions. But they were not put in the Referendum; they figured in no election manifesto; no politician can claim a democratic mandate to answer them. I say they cannot be for an unelected Prime Minister.

Let me acknowledge this.

Although the argument I am putting forward is a procedural one – should Parliament or the Prime Minister make the decision about triggering Article 50 – I am interested in it because I believe the sovereignty of Parliament is substantively engaged. And I can only say that if I am prepared to contemplate that Parliament might take a different view to the Prime Minister.

But to contemplate this is not to urge Parliament to ignore the outcome of the Referendum. It is to urge Parliament to consider it in the context in which it arose. That context includes a number of assurances – of a points-based immigration system, of £350m extra to spend on the NHS, of VAT cuts on fuel – each of which has already been disavowed by the Prime Minister. Is the falsity of a representation relevant to the quality of the consent it induces? For legal readers of Counsel, there is only one answer. It includes the imprecision of the Referendum question and the competing accounts of Brexit that were given. It includes the fact that Parliament enacted only an advisory Referendum. It includes the enormous importance to our life as a nation of whether we are inside or outside the EU. And it includes the small margin of victory. Each of these factors must be weighed in the balance, alongside the democratic importance of adhering to the outcome of a hard-fought referendum campaign.

This weighing exercise is not one for an unelected Prime Minister. Parliament, with the roving democratic mandate given to its Members, must find a resolution. It should decide what to do with the result of the Referendum. And those who value democracy should hope that the Divisional, and then the Supreme Court, will direct that it does.