In the foyer of the European Court of Justice building in Luxembourg there's a copy of Eduardo Paolozzi's statue of Sir Isaac Newton, on loan from the National Galleries of Scotland. Curiously, the artist signed it on the reverse. Which means that the first thing the august judges of Europe's supreme court see upon arriving for work is Newton's backside.

It's a posture that would appeal to Boris Johnson. He too wants to give the ECJ the bum's rush. He regards the court as an instrument of “colonial” domination, imposing an alien legal code on Britain. The main reason he wants to “chuck Chequers” is because Theresa May's latest Brexit plan leaves the European Court of Justice as the ultimate authority on trade disputes. Actually, on this at least, the bouffant Brexiteer is correct.

It's more complicated, of course, everything to do with Brexit is. The latest backstop proposal for resolving the Irish border problem seems to involve Britain remaining in the Customs Union for an indefinite period and for Northern Ireland to remain in regulatory alignment with the European Single Market. Brussels insiders, like the Labour MEP, David Martin, of the parliament's International Trade Committee, believe a deal along these lines has already been done behind the scenes. It remains only for the Brussels negotiator, Michel Barnier, to announce it, in great fanfare, this week.

But if my soundings in Brussels are correct, there is almost zero chance of it being agreed – at least by the Brexiteers. This is because, if Britain remains even partially in the single market and the Customs Union under the so called “hybrid backstop”, that leaves the UK still subject to the European Court of Justice. And these people don't mess about.

The top legal adviser to the European Court, Advocate-General Eleanor Sharpston is about as tough as they get - she's a karate black-belt for a start. She made it clear that there's no bucking the ECJ. “This court decides what the single market rules are, and that isn't going to change”. Theresa May can try to claim that Britain is not under the “direct jurisdiction” of the ECJ – perhaps by having the UK Supreme Court act as intermediary – but the inescapable legal reality is that it is. The ultimate arbiter for disputes about the European Single Market and the Customs Union is the Luxembourg bench.

Boris Johnson understands this. He says that, under this week’s proposed deal: “We cannot escape the EU laws and ECJ until they allow us to – which they may never do”. He goes on to say that this makes Britain a “colony” which is of course ridiculous. There is a world of difference between a court that deals with disputes over trade and related matters, and the supreme legal authority of a nation state.

Whenever countries join a rules-based international trading system they agree to share sovereignty. The World Trade Organisation , the hard Brexiteers' hard backstop, also has an arbitration procedure. The European Free Trade Association, has a court. Thai doesn't mean that members of EFTA or the WTO cease to be independent countries. Perhaps the greatest mistake made by Theresa May in these entire negotiations has been to go along with the fiction that Brexit means “taking back our laws”. We never lost them.

Even the UK government's own White Paper on Brexit made this clear in February 2017 when it said that the UK parliament “remained sovereign throughout our membership of the EU”. It went on to say that “it didn't always feel like that”, but the constitutional situation has never been in doubt. We never lost control of our laws, except in very narrowly defined areas. The demonising of the European Court of Justice has been a disastrous error of rhetoric, which has led many people to believe the canard that – as the Foreign Secretary Jeremy Hunt put it at the Tory Conference in Birmingham– the EU is a “prison” like the old “Soviet Union” from which Britain is “escaping”.

This equation of the EU with the USSR, which has become commonplace among Tory eurosceptics, has caused genuine outrage across the European Union – especially in central European countries which actually experienced soviet domination. Try suggesting to someone from a Baltic state, like Lithuania, that the EU is prison. They'll tell you, forcefully, that it was the European Union that helped them escape from communist domination. First by giving them a model of freedom, prosperity and human rights, and second by allowing them to become members of a union founded on the autonomy of independent nations.

There was a palpable change of mood in Brussels last week following the rhetoric of that Tory conference. Britain's friends in the Brussels have mostly given up trying to defend UK ministers. Officials, politicians, and Brussels commissioners just want an end to this whole demeaning Brexit process – and they don't much care how. They've other, more important things on their minds, like populism, Italy, Putin, Trump.

And I have to say, there’s very little support in Brussels for Nicola Sturgeon's call to delay the implementation of Article 50 next March. That would need the agreement of all 27 remaining states and officials now believe that is most unlikely. This is partly because EU governments just refuse to prolong the agony. This week's deal looks final.

And it poses very serious problems for Scotland. If Northern Ireland remains in the single market, this will be a huge attraction for firms wishing to gain the benefits of working within the EU without leaving the UK. It gives the North a massive competitive advantage over Scotland. Nicola Sturgeon is right to demand parity. But there's no way she is going to get it. Senior Brussels commissioners dismiss out of hand the idea of Scotland getting a similar deal. They won't even talk about it – I've tried.

There is some sympathy in the European Parliament for Scotland’s plight: being forced out of the EU against its will. According to David Martin, there's now a real willingness to help Scotland rejoin the EU, if it were to become independent. But that is very much for the future. The EU only deals with member states, in this case the UK, and right now they just want rid the lot of us.

My problem is that I can't see how the UK parliament can endorse this week's hybrid backstop. It may well be that a technical solution to the issue of Irish border checks is not far off. There are already health and environmental checks on agricultural goods and food coming from Northern Ireland to Britain. This could be the basis for a future “frictionless border” between Northern Ireland, which remains partially in the single market, and the UK which remains largely out of it.

But the DUP are having none of it. Britain remaining for an indefinite period in the Customs Union is a non-starter for Tory Brexiteers. The SNP must oppose NI exceptionalism and Chequers2 doesn't meet Labour’s “six tests”. Britain’s been asking for the impossible. If you remain even partially in regulatory alignment you must accept ECJ rulings. As with Paolozzi's statue, that's the bottom line.