The corollary is that for many unionists, it is one thing for the U.K. and Ireland to agree that there should be no physical controls policing the border, something London has committed to. But many senior unionists have voiced fury that, by agreeing to the backstop and its conditions of Northern Ireland being bound by EU and not U.K. law, the May government appeared to accept that Northern Ireland and the Republic of Ireland could not even be two distinct jurisdictions in principle. In effect, in their view, May had traded away that principle in response to threats of violence against anything that polices the border.
This gets to Brexit’s most basic question: Whose law applies in whose territory? The backstop means that even after Britain leaves the EU, the bloc’s law extends beyond its borders into another jurisdiction.
According to one of the May-administration officials I spoke with, there are two main practical problems on top of the problems of principle.
The first centers around the scale and scope of the checks that will be required under the terms of the backstop. These checks, on industrial goods, animals, and agricultural produce, will be carried out within the U.K., at the sea border between the British mainland and Northern Ireland, so as to avoid them taking place at the land border with the Republic of Ireland.
In this scenario, to move industrial goods from, say, London to Belfast, businesses will have to produce a document (a U.K. movement certificate) to prove the goods’ origin, an onerous new requirement on both companies and the authorities, in the view of its critics. But not as onerous as that for food, which will be checked in full to ensure that they are properly documented, and undergo physical inspection rates of up to 100 percent. Remember: This is for produce moving within the United Kingdom.
Read: The Good Friday Agreement in the age of Brexit
What frustrated the May government was the fact that the scale of the proposed checks was far greater than that of checks on goods from some non-EU countries, such as New Zealand, which struck a “veterinary agreement” with Brussels that means only 1 to 10 percent of its agrifood exports to the EU are physically checked (they still have documentation checks).
The second practical area of concern is that the backstop includes Northern Ireland in the EU’s value-added-tax (VAT) zone, which means that if the rest of the U.K. overhauls its VAT system, a financial gulf would be created within the country. Under EU rules, no country can lower its standard VAT rate below 15 percent. The VAT rate in the U.K. is currently 20 percent, but if the government wanted to move outside the EU band, it could not apply its new rules to Northern Ireland.
Finally, and perhaps the core problem of the backstop, is that it is indefinite. Many of the above problems could be swallowed, its critics say, if it were just a stopgap, and legally limited in how long it would last. Critics argue that it completely untips the balance in what comes after Brexit: negotiations over the future relationship between Britain and the EU, and the arrangement that replaces the backstop.