Constitutions are usually invoked by the losing side in a political argument. Appeals to the rule book signal that a cause, while not hopeless, is short of weapons more practical than hope.

So it is with those who would delay or halt Britain’s departure from the European Union. The supreme court notionally helped them by upholding a high court ruling that the government must seek parliament’s approval before activating article 50 of the combined EU treaties – the point at which Brexit is almost certainly irreversible. But it looks unstoppable already.

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The judgment does not make Brexit less likely, but it does make Brexit more parliamentary. It puts the referendum result in its place: politically irresistible but not a licence for unchecked executive power; a clear instruction from the majority but not a dissolution of minority opinion. This news is inconvenient for Theresa May but healthy for democracy.

May does not doubt that MPs will trigger article 50. They have already backed her proposal to get it done before the end of March, and by a majority of 372. That was a nonbinding vote, but there is no reason to think a binding one will produce dramatically different results.

Labour says it will table amendments attaching all manner of conditions, but the impact will be marginal. Plenty of opposition MPs are persuaded – some on principle, others because they are intimidated by the volume of leave voters in their constituencies – that the referendum result demands prompt satisfaction.

Jeremy Corbyn’s party is engaged in the Brexit debate like a dog on a football pitch – eager to be where the action is without knowing in which direction it should be running. Liberal Democrats and Scottish Nationalists are more focused but lack the numbers to cause a major obstruction.

Most pro-European Tory MPs still hope their concerns will be heeded by May behind closed doors. They recognise that she rates personal loyalty above almost any other virtue, and are thus reluctant to make trouble in public. I have heard remainer Tories say they are encouraged by what they have heard in private communications with No 10. But there is no tangible evidence that their softly-softly approach has any effect; the loudly-loudly manners of hardline Brexiters set the national tone.

There is a large parliamentary caucus to support a judicious enactment of the referendum mandate – one that is consistent with the technical requirement to quit the EU, while proceeding delicately through the detail so as not to vandalise economic and diplomatic relations with continental neighbours. But it is scattered across different parties, with no headquarters and no leader.

If there is parliamentary resistance to May’s Brexit vision it is unlikely to be organised around article 50. The more promising battlefield is the “great repeal bill” that the government has promised in spring. This will be a monstrously baggy piece of legislation. It must migrate the entire edifice of European law, currently applicable by virtue of EU treaties, on to the statute books as free-standing UK law. This has to be done to avoid legal black holes when Britain’s treaty commitments expire.

This same law will also create a mechanism for ministers to expunge features of the European legacy post-Brexit, at their leisure. This involves “delegated powers” by which the government can change statutes without running the full gauntlet of MP scrutiny. (These are sometimes called “Henry VIII clauses” in memory of his attempts to merge royal whim with the law.)

If the “great” repeal device includes rigorous checks and balances, parliament will be bogged down for years. But if it is designed for efficiency, the government will acquire a formidable weapon for erasing laws at a stroke.

That prospect is sure to offend MPs from all parties. It is sure to trample on the remit of devolved assemblies. The Lords will guard its backstop powers jealously, causing many Tories to discover a sudden appetite for reforming the upper chamber. The whole thing is going to get messy.

These coming conflicts and the supreme court case have a common root: tension between the political heft of a plebiscite and the constitutional fact of parliamentary sovereignty. The mandate of the referendum is newer; the mandate of MPs is better.

Brexiters may brandish “the will of the people” as if it were a machete cutting through thickets of opposition, but their sharp rhetoric has legal limits. As the high court noted in its ruling last year, quoting the jurist AV Dicey: “The judges know nothing about any will of the people except insofar as that will is expressed by an act of Parliament.”

Ministers sounded more deferential to that opinion on Tuesday than they did after their first defeat. In November, May’s inability to voice distaste for the hounding of judicial “enemies of the people” by Brexit-hungry newspapers looked like complicity in the attack. That caused alarm in some EU capitals, notably Berlin, where the totalitarian idiom is not bandied about so lightly. Downing Street had to give private reassurance of Britain’s enduring respect for judicial independence.

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May is more confident of MPs’ support for Brexit now, but not necessarily more patient with dissent. She sees the referendum as an instruction for government ranging beyond the question on the ballot paper, and treats the result as an expression of economic and cultural insecurity – a howl of rage against a metropolitan liberal ruling class.

May’s Brexit mission is a project of national salvation, not some technical exercise in treaty revision. Aligning herself with this maximalist definition of the referendum is a way to grab electoral legitimacy. It retrofits a personal mandate on to her leadership, since she came to the top job without one.

But the prime minister is not the figurehead of a revolutionary movement. She has permission to govern only because her party commands a majority in the Commons. Her insight into the “will of the people” is no greater than anyone else’s, nor any more constitutionally binding.

Those are the rules. It might be frustrating to be reminded of them but if the institutions of a democracy did not sometimes restrain rulers, they wouldn’t be doing their job. The supreme court has proved it is up to the task. Now it is parliament’s turn.