The papers are very excited about Theresa’s May announcement of a bill to begin the legal process of Brexit. “May fires Brexit starting gun,” the Sunday Times says. “At last Brexit begins!” squealed the Sunday Express. "A hugely symbolic move" the Telegraph concluded.

It turned out they were right, even though they didn't know it. May confirmed in an Andrew Marr interview this morning that she'd trigger Article 50 by the end of March. But none of that had anything to do with the legal announcement, which simply followed the presumed model for how to disentangle EU and UK law.

No-one expected any mechanism for the legal issue apart from what May is proposing. In a debate that is beset by disagreements, it is one of the only things people agree on. There is some silliness being said today that this will be difficult for hard Brexit supporters on the right of the Tory party to stomach. Actually, hard Brexit people have always proposed what May is doing and soft Brexiters have agreed with them. The distinction between the positions is that hard Brexiters don’t see how many problems even this simple solution raises.

May’s plan is essentially a bridge between legal status quos. An awful lot of EU law was implemented in the UK by adding it to the the European Communities Act 1972, which basically said that we would abide by EU law. May’s plan - sometimes called ‘snapshoting’ or ‘grandfathering’ - involves passing a new repeal bill which would incorporate all of that law into British law, then cutting the automatic legal link with the EU and repealing that which we don’t like at our leisure further down the line.

It’s the most elegant possible solution for the issue of how to pull apart four decades of overlapping legal continuity. But it isn’t harmless. It'll be one of the most dangerous pieces of law this country has ever produced.

Firstly, and very few people have realised this yet, it constitutes an powerful form of renewed devolution for Scotland and Wales. There are areas of devolved competence - agriculture for example - which are mostly governed by EU law. Sure, the devolved assemblies technically have power here, but in actual fact they, like Westminster, must do what Brussels tells them. Unless there is something in that repeal bill which says those powers are returning from the devolved assemblies to Westminster, it adds up to a very substantial act of renewed devolution. Watch Sturgeon in particular very carefully. Despite the Brexit bluster, she actually has a lot to gain out of what’s happening.

Secondly, snapshoting the European Communities Act doesn’t actually fix the problem it is designed to fix. EU law is all over the place - not just in the 72 Act. It covers areas like discrimination, public procurement and right of equal access. Take the Equalities Act. Most of its provisions, say on race or gender discrimination, were UK law. But the bit on age discrimination was European law. It's like this all over the place: a mess. Actually untangling EU and UK law will take years and is much more complicated than just copying and pasting the original Act.

Then take regulators. A lot of that EU law is recognising European regulators. If we copy and paste that law, we’d still be governed by those regulators, which we presumably don’t want to be. And presumably they’re not too keen on using resources to regulate a country which is no longer a member state either.

This is a serious issue. We do not have the time, the money or the resources to create countless regulators in the two-year Article 50 timetable. And petitioning Europe to allow them to continue regulating us not only makes a mockery of Brexit, but allows them another advantage in negotiations.

Some Brexiters suggest throwing the problem to the courts - indeed that was the solution proposed by the inane report published by the Centre for Social Justice yesterday. They said the courts should rule on maintaining those regulatory standards until Britain had had time to set up its own regulators.

This argument was taken apart by James Chalmers, regius professor of law at the University of Glasgow, in the way you might swat away a fly. Take the European Medicines Agency, he said, which happens to be based in London. Pharmaceuticals firms, many of which are based in the UK, need to submit results to the agency or they can’t progress with testing and production. What exactly is it they’re supposed to do in this situation? Go to court and show them the results? It’s a nonsense.

What will they actually do? Obviously they will move to somewhere in Europe. A massive British industry, at real risk.

Then there are property rights. Intellectual property rights, for example, almost all come from Europe. We may need to pay compensation to those who lose these property rights. We can put that on the tab with the price tag of creating all those regulators, but it’s starting to add up. And it’s starting to look very complex and difficult to resolve in the crushingly tight timetable we have.

But all the problems pale in comparison to the key danger in the bill: sovereignty. This is being sold as a way to secure parliamentary sovereignty but it is also a threat to it.

EU law was turned into British law usually using statutory instruments, little mechanisms which allow you to change the law without a debate and legislation in parliament. And the repeal bill will allow ministers more statutory instruments. To quote the Tory announcement:

“The repeal bill will include powers for ministers to make some changes by secondary legislation, giving the government the flexibility to take account of the negotiations with the EU as they proceed.”

This is fair enough - it’s the only way you could make it work in practice. But it means our rights and industrial and environmental standards are now at risk as never before. Before, a government couldn’t dismantle a right because it was protected by Europe. And even if they could, it would cause an almighty stink in the press and parliament, where repealing an Act or amending it would trigger debate.

Now 40 years of law is just sat there, utterly vulnerable, and ministers will have all the power to mess with it, on a rainy Friday afternoon, when no-one’s looking.

You can see the ministerial jitters over this already, because eventually people are going to realise how severe the democratic danger is. David Davis commented on it in the notice of the repeal bill. “To those who are trying to frighten British workers, saying ‘when we leave, employment rights will be eroded’, I say firmly and unequivocally ‘no they won’t’,” he said.

That promise isn't worth the paper it’s printed on. Whenever a minister hands himself powers, he will promise that nothing will change. There is never a worse moment to believe him.

It would be dangerous for ministers to have so much power in the first place, but never as dangerous as it will be at that moment. Because after this bill comes into force British negotiators will do into trade talks with other, much more powerful countries. And those countries will want us to reduce our standards. They will want us to reduce our data protection standards, our chemical safety standards, our health regulation standards: the list is endless.

The pressure on the UK government will be huge. It will urgently need to sign trade deals to show stability. Foreign negotiators will see their position of relative strength and use it to drive a hard bargain. British negotiators will be incentivised to accept those demands. And ministers will be in an ideal position to deliver on them.

May’s announcement is just admin. Anyone would have followed this model. The crucial issue is how she’ll do it. Now the govt has confirmed the snapshot model, it needs to map out the democratic safeguards it will put in place for what is, despite the Brexit triumphalism, a uniquely dangerous moment for British sovereignty.

Ian Dunt is editor of Politics.co.uk

The opinions in politics.co.uk's Comment and Analysis section are those of the author and are no reflection of the views of the website or its owners