The New Brexit Deal Explained

The knotty details of Prime Minister Boris Johnson’s new Brexit deal with the European Union are contained in 64 pages of revisions to the old withdrawal agreement, and an accompanying road map to future relations.

After days of shadowy negotiations, the documents set out how Mr. Johnson’s deal differs from the one struck by his predecessor, Theresa May, which went down to a string of humiliating defeats in the British House of Commons.

These are the provisions that will determine whether Mr. Johnson’s deal meets the same fate. If the deal passes, they will shape Britain’s relationship with other European countries for a generation.

The biggest roadblock: the Irish border

For Britain, the thorniest part about leaving the European Union has proved to be the Irish border, an invisible line between Northern Ireland, which is part of the United Kingdom, and the Republic of Ireland, a member of the European Union.

As it stands, the border is untouched by customs posts or physical checks, because both regions, as part of the European Union, are in the same customs union and single market. But that will end after Brexit, risking the return of a border that helped provoke a long and deadly sectarian dispute on the island.

Mrs. May’s solution was the so-called backstop. It kept all of Britain in the European customs union, possibly indefinitely, forcing it to impose the same tariffs as other European countries. And it required Northern Ireland to hew even more closely to European single market rules.

That was anathema to hard-line Brexiteers, and also to Northern Irish unionist lawmakers who care deeply about the bond between Britain and Northern Ireland and detest any divergences in trading rules between the two.

So Mr. Johnson tried to find another solution, namely killing off the backstop but adopting different versions of some of its most contentious features.

What replaces the backstop?

Mr. Johnson’s plan — unnamed, as yet — would pull the whole United Kingdom out of the European customs union. That was a big victory for Brexiteers, opening a path to Britain striking its own trade deals, including with the United States.

It is also supposed to allay unionists in Northern Ireland because that region would legally be part of the United Kingdom’s customs territory, allowing it to retain its close ties to Britain and to benefit from future trade deals.

But the only way to avoid checks on goods passing from Northern Ireland into the Republic of Ireland was for the north to apply the European Union’s rules and procedures on tariffs — the same ones the Republic of Ireland follows. Mr. Johnson’s deal also keeps Northern Ireland aligned with European single market rules on industrial products and agricultural goods.

In practice, that meant that, rather than putting a border on the island of Ireland, Britain would have to put one in the Irish Sea, and impose regulatory and customs checks for items passing from Britain into Northern Ireland. Some analysts said that would create a separation of sorts between different parts of the United Kingdom, a proposal that Mrs. May said no prime minister could countenance.

Mr. Johnson has tried to mitigate the effects of that Irish Sea border with a system of rebates that would counteract higher European Union tariffs. Some goods, like personal items being carried by someone moving between Britain and Northern Ireland, would also be exempt from tariffs.

So far, though, this new system of checks has proved too much to bear for unionist lawmakers from Northern Ireland, who have refused Mr. Johnson’s deal and could ultimately be its undoing.

The backstop could last forever. What about the new plan?

Another major objection to Mrs. May’s backstop plan was that elected leaders in Northern Ireland, the region most affected, had no say in what trading rules they would follow or how long they would last.

On this point, Mr. Johnson won a major concession from European leaders. The new deal gives Northern Ireland’s elected body a chance to weigh in on the arrangements and potentially spurn its obligations altogether.

But Northern Ireland could not opt out of European trading rules immediately. Those would take effect at the end of a transition period in 2020 and remain in place for four years before anyone in Northern Ireland could object.

And even then, the Democratic Unionist Party could not, on its own, pull Northern Ireland out from under European rules. (The voting procedure is complex, but lawmakers from other parties in the Northern Ireland Assembly would have to agree.) Unionist lawmakers suggested on Thursday that that was a deal breaker.

The assembly could keep voting on the agreement every number of years. And in the event the assembly did decide to pull out of the deal, the European trading rules would remain in place for two years after that so the parties could try to find a different way of avoiding a hard border.

Level playing field? Leave it to later.

A major source of concern in these negotiations has been coming from three little but critical words on the functioning of one of the richest single market in the world: level playing field. For member countries of the European Union, this means following common product standards for food and merchandise.

Once it is out of the bloc, Britain could be tempted to throw out the rules or water them down. For while they are seen as among the world’s best for the protection of consumers and, increasingly, the environment, they can also be quite stringent and costly to businesses.

Agreeing to a level playing field, as Mrs. May was prepared to do, would allow Britain and the European Union to negotiate a free-trade agreement quickly and eliminate much of the red tape that would come along with a hard Brexit.

But Mr. Johnson has clearly said he is not interested in adhering to European rules when it comes to goods, a position that has sparked outrage.

The issue is of such concern that the new agreement entirely omits it. Instead, discussion of a level playing field has been relegated to the nonbinding Political Declaration between the two parties, meaning it can be changed in future.

Critics were quick to see environmental and other loopholes in this detail that could drive down the quality (and, some would say, costs) of certain goods in Britain.

What’s the future for the U.K. and E.U.?

This may be the end of negotiations (may be!) but it’s also the beginning of talks for a new chapter in Britain’s relations with the European Union. The future relationship will be a matter of debate and negotiation that will most likely take years to crystallize.

In a nonbinding statement, known as the Political Declaration, they agreed “to work together to safeguard the rules-based international order, the rule of law and promotion of democracy, and high standards of free and fair trade and workers’ rights, consumer and environmental protection, and cooperation against internal and external threats to their values and interests.”