President Joe Biden’s sweeping executive order on immigration will likely reduce the number of migrants crossing the U.S.-Mexico border and making their way to New York City, policy experts said.

The new measure is unlikely to affect migrants already in New York City, though some observers said the changes could upend family reunification efforts by making it harder for newcomers to follow family members here.

“Whatever we can do to slow the flow and finance and allow people to work, I’m all for it,” Mayor Eric Adams told reporters on Tuesday.

The executive order comes as election year polls show voters are increasingly on edge about immigration and border security. More than 200,000 migrants have arrived in New York City alone since 2022, and more than 65,000 migrants are staying in shelters across the five boroughs, according to City Hall.

Under the new rules, border officials can rapidly turn away asylum-seekers — effectively closing the border — when illegal crossings exceed a certain level. The Biden administration also announced other steps aimed at resolving immigration cases more quickly.

The changes mark the Biden’s toughest border restrictions yet after attempts at immigration reform by Congress have repeatedly failed.

“I’m hopeful in this moment that we will see some real relief in terms of the amount of people that we are getting in through the front door,” said Deputy Mayor Anne Williams-Isom, a City Hall leader who is managing the migrant crisis.

Migrants who unlawfully cross the U.S.-Mexico border outside of a port of entry are generally ineligible to seek asylum under the new rules, which do not apply to unaccompanied children, victims of severe trafficking, lawful permanent residents or other immigrants with visas or legal permission to remain in the U.S.

Other exceptions will only be made under “exceptionally compelling circumstances,” such as if a migrant or a member of their family traveling with them is facing an acute medical emergency, “an imminent and extreme threat to life or safety.”

The new rules will also not apply to migrants who seek asylum through a federally approved process at a port of entry.

But the American Civil Liberties Union is expected to challenge the order in court, which could delay or bar it from going into effect.

Lee Gelernt, deputy director of the ACLU’s Immigrants’ Rights Project, said in a statement: “It was illegal when Trump did it, and it is no less illegal now.”

Many new migrants seeking shelter in the city arrive within days of crossing the U.S.-Mexico border, according to advocates and aid workers.

“What happens at the border has an effect on what happens in New York,” said Josh Goldfein, a senior Legal Aid Society attorney monitoring the city’s migrant shelters. “But it’s not a direct correlation.”

Margaret Martin, who co-directs the Immigrant and Refugee Services Division at Catholic Charities of New York, said the policy is likely to stem the influx of asylum-seekers entering the United States and coming to New York.

But, she added, “so many questions” remain about the new measure.

“We’ll see what it actually looks like in practice,” Martin said.

The new temporary rules take effect when the seven-day average of daily illegal border crossings reach 2,500 or more — which happens regularly.

According to the administration, the rules are intended to be a temporary reprieve as border crossings surge. They remain in effect until the seven-day average of daily illegal border crossings dips below 1,500, and the passage of 14 calendar days after that threshold is reached.

The policy doesn’t directly pertain to more than 65,000 migrants currently living in local shelters and the untold number of others living in other accommodations throughout New York City.

But immigration advocates and scholars say it could prevent migrants currently living here from reuniting with family members who planned to seek asylum in the United States and join them later on.

Marciana Popescu, a Fordham University professor studying local asylum-seekers, said the new rules could incite fear among migrants currently living in the city, who may wonder, “This is one executive order. What comes next?”

Another recent Biden administration policy could affect migrants currently in immigration court proceedings in New York City.

A new initiative aims to fast-track the immigration court process for asylum-seekers, allowing judges to more quickly approve eligible migrants and deport others.

The administration will create a new list of immigration court cases fast-tracked for review, which attorneys colloquially call a “rocket docket” and which the Biden administration calls the “Recent Arrivals” docket, with a goal for judges to decide the cases within 180 days.

The new docket will target single adult migrants who illegally cross the border outside of authorized ports of entry.

Spokespeople for the Executive Office for Immigration Review did not immediately respond to a request for comment on details of the new docket rule and when it will go into effect.