An abandoned border control post at the entrance to Muff, in the Republic of Ireland.
LONDON — The Irish backstop … convenient shorthand for a devilishly complex subject. It sounds almost like a fence, but the issue is about not having a fence at all — an apt paradox for a problem that may not have a solution.
And it has become one of the overriding sticking points in Brexit, Britain’s halting, seemingly interminable effort to leave the European Union.
Government officials debate it daily, in London and on the Continent, and ordinary Britons and Irish people are discussing it, too, if only to say that they don’t understand what it means.
Why is a backstop needed?
In short, it is a way to avoid building a physical border, with checkpoints for goods, on the boundary between Ireland, a European Union member country, and Northern Ireland, a part of the United Kingdom.
Simple, right? In fact, achieving that goal when Britain leaves the bloc, and doing it in a way that satisfies both the British Parliament and European negotiators, turns out to be a bit like trying to solve a jigsaw puzzle while blindfolded.
Don’t European countries check imports?
In global terms, goods crossing from one nation to another often have to undergo checks for two main reasons: to make sure that the importer pays customs duties, or tariffs; and to make sure that the merchandise meets the importing country’s standards. (Think of it this way: Did you pay the tariff on that toaster, or car, or sausage? And is it safe to use, or drive, or eat?)
However, the European Union has done away with all of that inside the bloc, eliminating barriers — both physical and like the examples above — that might impede trade between its 28 member countries.
Instead, the member nations have a customs union, meaning that they do not charge tariffs on one another’s products. And they have a single market, sharing a single set of product standards.
In addition, the 1998 Good Friday agreement that helped end sectarian violence in Northern Ireland guaranteed that there would not be a hard border between that part of the United Kingdom and the Republic of Ireland. Officials in Ireland, in Northern Ireland and in the rest of the European Union all insist that must not change, and no faction in the British Parliament wants it to change.
What Is Brexit? A Simple Guide to Why It Matters and What Happens Next
The basics of Brexit, the troubled plan for Britain to quit the European Union.
What changes when Britain exits the E.U.?
Britain is scheduled to leave the European Union on March 29, but under the agreement that Prime Minister Theresa May has negotiated with Brussels, there would be no immediate change in trade. Britain would remain in both the customs union and the single market until at least the end of 2020, during which Brussels and London would attempt to negotiate a permanent trade relationship.
At that point, if no deal has been reached, either the transition period could be extended until 2022 or the Irish backstop could come into effect. The backstop could also come into play if an agreement has still not been found by 2022.
A long-term trade deal with the European Union could mean leaving both the customs union and the single market, which is what Mrs. May proposes and what the hard-line pro-Brexit faction wants. Britain would be able to strike trade deals with other parts of the world, and to opt out of European standards.
Under current rules, that would mean checking goods flowing across the Irish border. And with today’s technology, that would require physical barriers and border checks.
So, as it stands, Mrs. May’s pact with the European Union provides that if Britain and the European Union cannot agree on a long-term trade arrangement that deals with the Irish border question, then either at the end of 2020 or at the end of 2022, the backstop would kick in.
So what is the backstop?
The backstop provision says that as long as there is no long-term trade pact, Britain would remain in the European customs union, and Northern Ireland would also be bound by many rules of the single market.
European leaders not only demanded the backstop, but they also insisted that it have no expiration date.
Britain could therefore be outside the European Union, with no voice in shaping its rules, but remain closely tied to the bloc indefinitely. To Mrs. May’s hard-line, pro-Brexit colleagues, that is a nightmare scenario that could leave Britain permanently powerless to determine its own trade destiny.
The prime minister could ignore the pro-Brexit factions in her party and cut a deal with the Labour Party for a “soft” Brexit that would, at minimum, leave Britain in the customs union. But that would risk alienating those who voted in the referendum to leave, and it would risk tearing the Conservatives apart, an outcome that many believe is Mrs. May’s greatest fear.
European officials have suggested that Britain could largely avoid the single market standards by having only Northern Ireland abide by those listed in the backstop, while a different set of rules could be adopted for the rest of the country. British lawmakers have rejected that out of hand because they say that it would create a virtual border in the Irish Sea, cutting off Northern Ireland from the rest of the United Kingdom and moving it closer to unification with the Republic of Ireland.
Mrs. May argues that the backstop might never go into effect, and that, even if it did, it would not be in place for long. Her government envisions a future system that would allow customs and standards checks without actually stopping and inspecting trucks or people at the Irish border — technology that does not yet exist.
What happens next?
This month, Parliament rejected Mrs. May’s agreement by a crushing margin, 432 to 202. Primarily because of the backstop, 118 of the 317 lawmakers from her Conservative Party voted against it, as did all 10 of the Democratic Unionists of Northern Ireland, whose support Mrs. May relies upon for her parliamentary majority.
On Tuesday, Parliament voted to direct the prime minister to return to European negotiators and demand an expiration date to the backstop, or a clause that would allow Britain to withdraw from it without the bloc’s approval.
But Brussels has insisted that it will not budge, and even if it made such a concession, it is not clear that a change would ensure passage of Mrs. May’s deal in the British Parliament.