Brexit Secretary David Davis. Photo: PA/PA Wire/PA Images

MPs today begin debating what was once grandly dubbed the “Great Repeal Bill.” The European Union (Withdrawal) Bill, as it is now more soberly known, is intended to avert legal catastrophe when Britain leaves the EU, by ensuring that the vast body of EU law currently applicable in the UK largely remains in place. So, in spite of its moniker, the Bill does not actually repeal very much. It gets rid of the European Communities Act 1972, which currently gives domestic effect to EU law, but goes on to heavily ameliorate the consequences of that repeal. It does so by, in effect, providing for a snapshot of EU law to be taken, as it exists at one minute to midnight on the eve of “exit day,” and converting it into UK law.

However, the Bill also recognises that a straightforward cut-and-paste approach would not work. Some EU law (e.g. that which relates to the single market and the customs union) is unlikely to be of any relevance post-exit, and will need to be repealed. Other EU law will need to be amended to make it fit for purpose following Brexit. Recognising that a great deal of surgery will need to be performed upon the body of EU law before exit day, and given that parliament will simply not have time to perform that surgery itself, the Bill hands the legislative scalpel to ministers, by investing them with delegated powers.

All of this is sensible. Indeed, it is imperative. If such a strategy were not adopted, then Brexit would amount to a legal cliff-edge—and falling over it would entail utter chaos, since it would open up enormous gaps in the statute book. However, the fact that the central aim of the Bill—that is, preserving EU law post-exit—is a necessary one does not place the Bill beyond criticism. And arguments to the contrary—in particular, suggestions in some quarters that objecting to the Bill equates to attempting to block Brexit—are entirely specious. Indeed, the Bill, in its present form, is profoundly problematic in legal and constitutional terms. It is an affront to parliamentary sovereignty. It eviscerates the separation of powers principle. And it risks destabilising the UK’s increasingly fragile territorial constitution.

The notion of “taking back control” was axiomatic to Leave campaigners during the EU referendum. Central to that notion was the idea of parliamentary sovereignty: of making the UK Parliament supreme again, free from interference by unelected bureaucrats in Brussels and meddling judges in Luxembourg. Viewed against this background, the Bill is little short of astonishing. Far from cementing the sovereignty of parliament, it would, if enacted in its present form, result in an unprecedented transfer of power away from parliament, by placing extraordinary authority in the hands of the executive government. That, in turn, would fundamentally undermine the separation of powers—which holds, among other things, that it is for parliament to make the law.

“One might expect such extraordinary ministerial powers to be accompanied by an extraordinary system of oversight. One would be disappointed”

That said, like many aspects of the British constitution, the separation of powers is not rigid, and it is far from uncommon for parliament to confer limited law-making powers on the government. But the Withdrawal Bill does not confer carefully demarcated powers: it invests the executive with immense law-making authority. As the House of Lords Constitution Committee puts it in a report published today, “The Bill weaves a tapestry of delegated powers that are breath-taking in terms of both their scope and potency.” Those powers include so-called Henry VIII powers, meaning that they can be used not only to amend EU law but also to amend, or even repeal, parliamentary legislation. Indeed, it is difficult to imagine wider executive powers: ministers are authorised to “make any provision that could be made by an Act of Parliament.” And it is plain that these powers will not be used merely to make minor, technical amendments to the post-exit statute book. The Bill, for instance, explicitly contemplates that ministers will be able to use their authority both to establish new regulatory regimes and institutions and to invest them with law-making authority. This amounts to a form of Henry VIII power on stilts.

One might expect such extraordinary ministerial powers to be accompanied by a correspondingly extraordinary system of parliamentary oversight and control. But one would be disappointed. A small number of matters will be subject to the so-called affirmative procedure, meaning that parliament will have to approve them—but since parliament cannot amend delegated legislation, the likelihood of outright rejection will be very slim indeed. Meanwhile, the vast majority of the law made by ministers under the Bill will be subject only to annulment by parliament, such that it remains in force unless parliament objects. But the chances of this are vanishingly small: it is nearly 40 years since the House of Commons rejected a statutory instrument. Calls for enhanced scrutiny—made by the Hansard Society and the Lords Constitution Committee, among others—have so far gone entirely unheeded. And although the exercise of these delegated powers is supposedly limited by a “sunset clause”—meaning that they lapse two years after “exit day”—ministers can choose what “exit day” means. They can even say (free from any parliamentary control) that it means different things for different purposes, thus enabling the sunset clauses to be circumvented.

“It is parliamentarians’ constitutional duty to scrutinise and improve this Bill”

As well as raising serious constitutional issues as to the relationship between Westminster and Whitehall, the Bill implicates relationships between London and the devolved capitals. The first ministers of Scotland and Wales have already described the Bill as a “naked power-grab,” on account of the fact that EU competences that would, by default, have flowed to Belfast, Cardiff and Edinburgh (because they concern devolved subject-matters) are to be diverted to London. In the light of this, it is likely that the Welsh assembly and the Scottish parliament will withhold their consent to the Bill. That consent is arguably required by the Sewel Convention, according to which the UK parliament will not normally legislate so as to adjust the devolution settlements absent devolved legislatures’ agreement. The Supreme Court made it clear in the Article 50 case brought by Gina Miller that there is no possibility of judicial enforcement of the Convention. But if the UK parliament seeks to press ahead in the face of opposition from the devolved assemblies, the political consequences for an already-fragile territorial constitution are likely to be profound.

It is difficult to overstate the constitutional difficulties raised by the Bill—difficulties that are exacerbated by the byzantine nature of its drafting, which in turn is likely to generate so much confusion as to compromise legal certainty and place the rule of law at risk. The EU (Withdrawal) Bill, for all that it might be convenient to pretend otherwise, is not just a technical matter of interest to legal anoraks. It is a constitutional statute of fundamental importance that will shape the British legal system for many years to come. The stakes are correspondingly high. It is parliamentarians’ constitutional duty to scrutinise and improve the Bill, and suggesting that any refusal to nod through this deeply flawed legislation would amount to frustrating the will of the electorate as expressed in the referendum is little short of absurd. Whatever a vote for Brexit meant, it was surely not a vote for the degradation of fundamental constitutional values.