The deal, which the Canadian government said would come into effect early on Saturday, effectively extends the so-called Safe Third Country Agreement (STCA) to the entire US-Canada border.

“The United States and Canada will work together to discourage unlawful border crossings and fully implement the updated Safe Third Country Agreement,” US President Joe Biden said during an address to the Canadian parliament in Ottawa on Friday afternoon.

But human rights groups said the move will not deter refugees and asylum seekers from trying to cross the 6,416km (3,987-mile) land border between the neighbouring countries but instead will push them to take riskier routes.

Here’s what you need to know about the agreement.

How does the new agreement work?

The White House said in a factsheet that the updated STCA would be applied “to migrants who cross between the ports of entry”.

The Reuters news agency reported on Friday that “according to a final rule set to be published in the US Federal Register, the revised agreement will apply to anyone who makes ‘an asylum or other protection claim’ in either country within 14 days of crossing the border.”

Separately, Canada also agreed to take in “an additional 15,000 migrants on a humanitarian basis” from countries in the western hemisphere, “such as Haiti, Colombia, and Ecuador, over the course of the year”, the White House said.

What rules governed the border before this?

Since 2004, the STCA has forced asylum seekers to make claims for protection in the first country they arrive in – either the US or Canada.

That meant that people already in the US could not make an asylum claim at an official port of entry into Canada, or vice versa, and allowed border authorities to uniformly turn people back at official land crossings.

But asylum seekers could make claims for protection once on Canadian soil, and that loophole pushed thousands to take informal routes across the massive land border between the two nations.

How many people were crossing into Canada outside official points of entry?

Last year, the Royal Canadian Mounted Police (RCMP) intercepted more than 39,500 asylum seekers who irregularly crossed the border into Canada, according to government figures. Nearly all of these crossings were into the eastern province of Quebec.

More than 9,500 people were intercepted in January and February of this year.

What about on the US side?

US Border Patrol processed 3,577 people who crossed into the US irregularly from Canada last year, CBS News reported, citing government data.

What effect will the new agreement have in practice?

The new deal means that both Canada and the US may turn back asylum seekers who are already in their respective countries, closing the STCA’s loophole.

In a statement, the Canadian government said the expansion means that “moving forward, foreign nationals who cross anywhere along the Canada-US border will not be eligible to make an asylum claim, unless they meet an STCA exception”.

“Otherwise, they will be returned to either the US or Canada to pursue their asylum claim, under the first safe country principle.”

How have rights groups responded?

“This is very dangerous,” said Frantz Andre, spokesperson and coordinator of Comite d’action des personnes sans statut, a Montreal-based group that provides support for asylum seekers and others without immigration status.

Andre said that despite being met with “a closed door” at the border, people will continue to come; They will simply be forced to take greater risks to find new ways to cross. “I have no doubt. People have come too far to go back. They know that the US is not a safe country,” Andre told Al Jazeera.

“This is not the Canada that I knew,” he said. “What is a humanitarian crisis has become political.”

The United Nations refugee agency’s representative to Canada said in a statement that UNHCR is aware of the changes and looked “forward to reviewing the details” with the Canadian government in the next days.

“UNHCR acknowledges that the US and Canada are facing significant challenges associated with the scale of arrivals of asylum seekers and migrants at their borders and urges all governments to keep in mind their obligation to provide haven to those fleeing conflict, violence or persecution,” Rema Jamous Imseis said.

Amnesty International Canada condemns the U.S. and Canadian governments’ agreement to expand, rather than rescind, the Safe Third Country Agreement in response to border crossings at Roxham Road.https://t.co/rMjPUvLpR7 pic.twitter.com/Dxk2SJ5hdI

— AmnestyCanada (@AmnestyNow) March 24, 2023

Why is this happening now?

Canadian Prime Minister Justin Trudeau has been under political pressure domestically to respond to an increase in crossings, particularly from conservative politicians in Quebec and at the federal level.

Of the nearly 40,000 asylum seekers who entered Quebec irregularly last year, most took a popular, unofficial route from the US state of New York known as Roxham Road. Most were from Haiti, Turkey, Colombia and Chile, CBC News reported.

For months, right-wing Quebec Premier Francois Legault has called for the closure of Roxham Road and for asylum seekers to be transferred out of the province, which he said could no longer handle the influx of arrivals.

This week, Legault sent his message to the rest of Canada, writing an open letter in The Globe and Mail, one of the country’s largest newspapers, headlined, “It’s time to close the breach at Roxham Road and enforce Canada’s borders.” During a news conference, Legault welcomed Friday’s announcement: “Thank you, Mr Trudeau,” the premier said in French.

Against this backdrop, Pearl Eliadis, a law professor at McGill University in Montreal, described the new deal as “a political statement to appease critics”.

“People cannot be physically prevented from coming across any other point of the border, near Roxham Road or elsewhere. This measure will just displace the problem and is a micro solution to a macro problem,” Eliadis said in a statement shared by the university.

How will the new agreement be enforced?

During a news conference on Friday, Trudeau said “police and border officers will enforce the agreement and return irregular border-crossers to the closest port of entry with the United States”.

But how exactly that will work remains unclear.

Asked how the RCMP intended to uphold the expanded deal, a spokesperson told Al Jazeera that the federal police force cannot say what resources are devoted to specific duties “for safety reasons and to ensure the integrity of our operations”.

Public Safety Canada, the federal ministry that oversees the country’s borders, did not immediately respond to Al Jazeera’s request for comment on Friday.

“Outside some incredible increase to what currently exists, I don’t think there’s any suggestion from the government that they have the resources or the capacity to patrol the entire border,” said Julia Sande, human rights law and policy campaigner at Amnesty International Canada.

“It’s just a matter of pushing people to more remote ports of entry,” she told Al Jazeera.

When will the new policy come into effect?

The Canadian government said the expanded STCA would come into affect at 12:01am Eastern (04:01 GMT) on Saturday.

Meanwhile, it remains to be seen if a ruling from Canada’s top court, expected within the next few months, could affect the new border rules.

The Supreme Court of Canada is currently weighing a legal challenge to the STCA, which claimants have argued violates the Canadian constitution and opens asylum seekers up to the risk that the US will send them back to their home countries.

“The idea that the government would seek to expand [the STCA] when we’re still awaiting a decision on that is just unconscionable,” Sande said. “This isn’t going to stop indirect crossings. People still need to seek safety if they’re not going to receive protection in the United States.”