LONDON — The ascension of a new prime minister in Britain has raised both fears and hopes (depending on the audience) that the country might leave the European Union cold turkey — no trade agreement in place, no political pact, not even a framework for further talks.
Three times this year, Parliament emphatically rejected the withdrawal deal that Theresa May negotiated with Brussels as prime minister, ultimately forcing her to step down.
She had flirted with the idea of a “no-deal” Brexit, but that may have been no more than a negotiating stance. When her back was to the wall, she agreed twice to delay the country’s departure, most recently to Oct. 31, to allow time for reaching an agreement.
Her designated successor, Boris Johnson, insists that while he intends to hammer out a better agreement, Britain will leave the union by that deadline, even if that means exiting without a deal.
[Read about the vote that put Boris Johnson in position to become the next prime minister of Britain.]
There are far more questions than answers available, but this is what we know.
What does “no deal” actually mean?
Relations among nations are exceedingly complex, with pacts on migration, customs checks, tariffs and product standards, among many things. Belonging to the European Union radically simplifies that: no trade or migration barriers between member countries, no differences in product rules, and unified trade pacts with the rest of the world.
In the absence of that system, Mrs. May and the bloc negotiated a withdrawal agreement that was almost 600 pages long, just to get through the next two years, until more permanent arrangements could be reached.
Leaving abruptly without a deal would mean new customs and tariff barriers, and would put Britain under World Trade Organization trading rules, which economists say are less advantageous and do not fill in all of the relevant blanks.
Various policies and systems would have to be built from scratch while long-term agreements are negotiated with the European Union, the United States and every other trading partner, which experts say would take years.
Why is “no deal” a big deal?
One economic authority after another has reported that a sudden no-deal Brexit would do deep, lasting harm to Britain. Even a careful, orderly departure like the one proposed by Mrs. May would depress economic growth compared with staying in the European Union, they contend.
Similar conclusions have been published by the International Monetary Fund, the Bank of England, the British Treasury and, most recently, Britain’s Office for Budget Responsibility, among others.
In fact, since voters approved Brexit three years ago, the mere prospect of it has harmed the British economy, economists and business executives say, as it prods companies, investors and job-seekers to go elsewhere.
Experts warn that crashing out of the bloc without a plan could bring travel disruptions and shortages of food, medicine and other goods.
But many ardent Brexiteers, including Mr. Johnson, insist that such fears are overblown, or just wrong. They contend that being free to negotiate its own trade deals, set its own immigration policies and stop paying into the European Union will benefit Britain in the long run. Some even wave off predictions of short-term pain.
“It is total nonsense,” Mr. Johnson said this month. “I prophesy very confidently that we will have a successful Brexit, the planes will fly, there will be clean drinking water and there will be whey for the Mars bars.”
What does Parliament think?
Parliament opposes a no-deal exit. In fact, that may be the only clear statement on Brexit that this Parliament has been able to make.
On March 13, the House of Commons took up a motion that Britain should not leave without a deal on March 29, which was then the deadline for withdrawal from the union. Over the government’s vehement opposition, lawmakers amended that to oppose a no-deal Brexit at any time, under any circumstances, and then passed the amended motion, 321 to 278.
The motion was nonbinding, but it was an embarrassment — one of a long series related to Brexit — for Mrs. May. It was widely believed that without the government’s pressure, the vote would have been more lopsided.
So what can Mr. Johnson do?
Mr. Johnson wants to strike an agreement of his own with Brussels by Oct. 31 — specifically, one without the controversial Irish border provisions in Mrs. May’s deal — but that may not be possible.
European Union leaders have said repeatedly that they will not reopen negotiations and that the deal they reached with Mrs. May is the only one they will consider.
Even if the bloc were bluffing, it is not clear that there would be time to draft a new pact by the deadline. The deal on the table was the product of almost two years’ negotiations.
But if Mr. Johnson is serious about leaving without a deal, all he would have to do is nothing. As things stand, the country will leave the European Union on Oct. 31 whether there is any agreement in place or no, under current British law.
Can Parliament prevent that?
Possibly. Parliament can change the law and instruct the prime minister to seek another extension.
There is debate about how binding that instruction would be on the prime minister, but it would not commit the European Union to an extension. All 28 heads of government would have to agree to push back the deadline, and some of them were reluctant the last time.
There has been much talk about the possibility that Mr. Johnson could prorogue, or suspend, Parliament as the deadline approaches, to prevent lawmakers from directing him to request an extension.
Prime ministers often suspend Parliament, simply to take a month or two off. Doing it requires the assent of the monarch, which in modern times has always been given.
But to suspend Parliament as a political tactic, and to involve Queen Elizabeth II in the dispute, would be unusual and controversial, and could anger some of Mr. Johnson’s fellow Conservatives. The party’s hold on power is tenuous, and if even a few of its lawmakers joined in a vote of no confidence, they could topple him.
On Thursday, the House of Commons voted, 315, to 274, to make it more difficult to prorogue Parliament. The vote, on a measure that still needs final approval, would require that the house meet before the end of October — at which point, presumably, lawmakers could vote to block a no-deal Brexit.