Fractured Foundations: How Brexit Handed the Devolved Nations a Constitutional Weapon

When the Leave campaign promised to 'take back control', the phrase was aimed squarely at Brussels. Few paused to ask which part of Britain would be doing the taking — or at whose expense. Years on from the referendum, the answer has become uncomfortably clear: it is Westminster that has reclaimed authority, and it is Edinburgh and Cardiff that feel most acutely the weight of that reclamation. Brexit, in a twist its architects did not anticipate, has become the most powerful argument the devolved governments have ever possessed.

The Repatriation Problem

Prior to Brexit, a significant body of EU competences overlapped with devolved policy areas — agriculture, fisheries, environmental standards, and aspects of public procurement among them. The expectation held by the Scottish and Welsh governments was that powers returning from Brussels would flow naturally to Holyrood and Cardiff Bay, in keeping with the devolution settlement's logic. What transpired was rather different.

The UK Internal Market Act 2020 became the flashpoint. Passed without the legislative consent of either the Scottish Parliament or the Senedd Cymru, it established mutual recognition and non-discrimination principles that effectively constrain devolved legislatures from diverging too far in their regulatory regimes. Critics in both Edinburgh and Cardiff were blunt: Westminster had not merely declined to pass powers downward — it had used Brexit as cover to claw back influence that devolution had previously insulated from central government reach.

The Scottish Government described the Act as a 'power grab'. The Welsh Government, traditionally more cautious in its constitutional ambitions, used language scarcely less pointed. Both withheld legislative consent. Westminster pressed ahead regardless, citing parliamentary sovereignty. The episode did not resolve a constitutional tension so much as crystallise it.

Holyrood's Sharpened Argument

For the Scottish National Party, Brexit has functioned as something close to a political gift — not because the SNP engineered the situation, but because it so thoroughly vindicated their warnings. Scotland voted 62 per cent to Remain. It was taken out of the European Union by a decision driven overwhelmingly by English votes. The democratic dissonance this produced has never dissipated.

The independence movement's central challenge had long been to make the case that Scotland's interests were structurally incompatible with Westminster governance — not merely different in emphasis, but different in kind. Brexit furnished that case with evidence that no pamphlet could have manufactured. Scottish ministers now routinely frame disputes with Whitehall not as political disagreements but as symptoms of a broken constitutional arrangement.

The practical frictions are real and multiplying. Scotland's distinct legal system, its different approach to public services, its ambition to maintain closer alignment with European standards in areas such as food safety and environmental regulation — all of these collide, with increasing frequency, against the gravitational pull of a UK-wide internal market framework that Westminster insists must hold firm. Each collision adds a data point to the independence argument.

Wales: The Quieter Rebellion

Wales presents a more nuanced picture, and one that receives less attention than it deserves. The Welsh Government under Labour has not pursued independence — polling in Wales remains considerably less favourable to separation than in Scotland — but it has adopted an increasingly assertive posture in its dealings with Whitehall. Brexit has been central to that shift.

Cardiff Bay's objections to the Internal Market Act were substantive, not merely procedural. Welsh ministers argued that the legislation undermined their ability to set higher standards in devolved areas, effectively imposing a race-to-the-bottom dynamic in which any part of the UK could undercut the regulatory choices of another. The concern was not abstract: Wales has sought to diverge on issues ranging from single-use plastics to agricultural support schemes, and the internal market framework creates genuine ambiguity about how far such divergence is legally and practically sustainable.

The establishment of the Independent Commission on the Constitutional Future of Wales — which reported in 2024 and concluded that the status quo was not viable — signals how far the conversation has moved. Independence was listed as one of three credible futures for Wales, alongside enhanced devolution and federalism. That such a commission was established at all, and reached such conclusions, reflects how dramatically Brexit has altered the constitutional weather.

Whitehall's Dilemma

The UK Government's position is not without logic. Maintaining a functioning internal market across four nations requires some degree of common standards and mutual recognition; the alternative risks regulatory fragmentation that could harm businesses and consumers alike. Ministers have argued, with some justification, that the devolved governments' complaints are partly political theatre — an attempt to leverage Brexit grievances for nationalist ends.

Yet the manner in which Westminster has managed these tensions has often been counterproductive. The decision to override legislative consent conventions, the use of secondary legislation to alter the devolution settlement without full parliamentary scrutiny, and the periodic bypassing of devolved administrations in spending decisions — including direct funding to local authorities in Scotland and Wales under schemes such as the Levelling Up Fund — have all fed a narrative of deliberate marginalisation.

Intergovernmental relations, long criticised as informal and opaque, were reformed following the 2022 review, but the new structures have not eliminated friction. The British-Irish Council and the new Interministerial Standing Committee meet with greater regularity, but substantive disagreements over post-Brexit policy — on subsidy control, on trade facilitation, on retained EU law — remain unresolved.

A Crisis Deferred, Not Avoided

It would be premature to declare a constitutional crisis already underway. Scotland remains within the United Kingdom, and the legal and political barriers to a second independence referendum remain formidable following the Supreme Court's 2022 ruling that Holyrood cannot legislate for such a vote unilaterally. Welsh independence is, for the time being, a minority aspiration. The union endures.

But durability is not the same as stability, and the conditions that might eventually produce a genuine constitutional rupture are being steadily assembled. Brexit created a democratic grievance that maps neatly onto national identity. It produced a governance framework that the devolved administrations regard as structurally hostile to their autonomy. And it has generated a series of practical disputes — over money, over regulation, over who decides — that keep the underlying tension permanently fresh.

The question Westminster has not yet answered satisfactorily is what kind of union it wishes to maintain, and on what terms. A union held together principally by legal constraint and parliamentary supremacy is a different thing from one sustained by genuine consent and shared purpose. Brexit did not create that distinction, but it has made ignoring it considerably harder.

Britain's post-Brexit constitutional settlement is not broken beyond repair. But it is under strain that no amount of intergovernmental reform communiqués will quietly dissolve. The devolved nations did not choose Brexit. They are, however, choosing what to do with the arguments it has handed them — and those arguments grow more sophisticated with every passing dispute.