AT the end of last week, there was the return of a familiar sound that had been subdued, if never entirely absent, during the pandemic. It was the cheery din of sabre-rattling by “senior EU diplomats” warning the UK of impending “punitive action” unless we mend our ways and comply with their demands.

Well, it’s nice to feel that things are getting back to normal. Because, goodness knows, no one would imagine that the small matter of having finally left the EU, a mere three years after the vote to do so, would prevent the bureaucrats of Brussels from continuing to dictate terms.

That, I think it’s reasonable to acknowledge, is fair enough when it comes to much of the UK’s engagement with the EU, since when we seek access to or co-operation with them on all sorts of things we do so on a so-called “third-country” basis. Whether you like it or not, we’re the ones who left the club.

On one hand, the point of leaving a club is that you no longer have to abide by its rules. On the other, it seems a bit daft to abandon certain kinds of sensible behaviour that do you some good and little harm, just because they are specified in those rules. Since everyone – including many who argued for Brexit at the time – seems to have forgotten, the case for leaving was to remove the EU’s political oversight, and restore the UK’s autonomy.

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The assumption – indeed, the position being offered – was that we would remain at least very closely aligned with the single market, if not (through membership of Efta or the EEA) within it, while having the freedom to seek trade deals elsewhere.

Theresa May’s mishandling of the terms of departure (since she was a Remain voter who disastrously misunderstood the Leave position in the first place) put the kibosh on that sensible ambition. I’d rather have stayed in the single market (though not the customs union), but I don’t at all blame the EU for insisting on its rules. Especially since it is not, despite its rhetoric, committed to free trade but about confining the benefits of it to its own members.

But the wrangling over the Northern Ireland protocol isn’t really to do with trade. It is true that the UK has not done much about setting up the infrastructure for border checks, which is what we undertook to do, and that, under the agreement we signed, that entitles the EU to introduce retaliatory trade tariffs.

But Lord Frost, the Brexit minister, has submitted around a dozen possible alternatives to physical border checks without having had any response from Brussels, even though the EU previously said it was open to “trusted trader” rules, and accepting equivalence status (without wholesale alignment) on issues such as agricultural products and food safety standards.

The Irish border is now one between the EU and a third country, but the idea that cross-border traffic – vital though it is to the economic health of both the Republic and Northern Ireland – endangers the integrity of the single market is preposterous. No one believes that the EU’s interest in it is because it threatens to undermine trade.

After all, it doesn’t police its other external borders in this way, let alone insist that those third countries have sole responsibility for setting up border infrastructure for the EU’s benefit. And there seems no immediate danger that contraband Australian kangaroo steaks or Japanese wasabi (to take two of the places Britain has signed trade deals with) are about to flood across the estimated 208 border crossings between north and south, bringing the economy of the EU to its knees.

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The EU is well aware of the sensitivities of the Irish border, the historical freedom of movement between the UK and the Republic and the fact that (despite differing regulations and duties on either side) policing of the border was historically much more a matter of security than economics. Imperfect though it is, the protocol placed requirements on the EU, too. It spells out commitments to the communities of Northern Ireland, and requires the EU not to undermine the guarantees of the Belfast Agreement.

An aggressive policing of the border obviously might make that more likely, which is why no UK government of any political colour would introduce it. It’s what necessitated the protocol in the first place – it was intended to offer a period during which a pragmatic and proportionate means of supervising cross-border trade could be introduced.

If there are to be new restrictions, or retaliatory tariffs, it’s the EU that’s insisting on them. That is, of course, their right. But it seems reckless to prioritise the protection of the single market – even though there is no evidence that a relatively relaxed Irish border poses any real risk to it – over the political stability of Northern Ireland.

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The EU’s use of the border as, at best, leverage in its negotiations with the UK or, worse, as a punitive measure to show that any country leaving their union will suffer for it, is irresponsible. Naturally, responsibility for any return to violence in Northern Ireland – something everyone wants to avert at all costs – could only be laid at the door of the fanatics and criminals who instigate it. But the EU has moral and, under the protocol, legal responsibilities that it is ignoring in to bolster its position in negotiating relatively piffling details of customs paperwork.

Anyone who thinks this is unfairly painting the EU as petty and reckless could look at the fact that Article 16 – which allows cross-border trade to be shut down – has, in fact, already been triggered, and it was by the EU, unilaterally. It did so at the end of January, not because of any breach of the rules by the UK, or because of any danger to the integrity of the single market or threat to health and safety standards, but to prevent the export of vaccines to Northern Ireland, at a time when it had become clear that they had bungled their own supply.

This was such an obviously shabby manoeuvre that even the EU realised that it was unjustifiable, and it was rescinded within a matter of hours. But it gives a pretty good indication of their willingness to play dirty.

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