CNN  — 

The expiration of a pandemic-era public health restriction that will significantly alter several years of US immigration policy has arrived, threatening chaos as an estimated tens of thousands of migrants mass near the US-Mexico border in anticipation.

Issued during the onset of the Covid-19 pandemic, Title 42 allowed authorities to swiftly turn away migrants at the US borders, ostensibly to prevent the spread of the novel coronavirus. But that changed late Thursday when the public health emergency and Title 42 lapsed.

Here’s how border crossings could be impacted after the order’s expiration:

Title 8 is back in effect

Title 42 allowed border authorities to swiftly turn away migrants encountered at the US-Mexico border, often depriving migrants of the chance to claim asylum and dramatically cutting down on border processing time. But Title 42 also carried almost no legal consequences for migrants crossing, meaning if they were pushed back, they could try to cross again multiple times.

Now that Title 42 has lifted, the US government is returning to a decades-old section of US code known as Title 8, which Homeland Security Secretary Alejandro Mayorkas has warned would carry “more severe” consequences for migrants found to be entering the country without a legal basis.

The Department of Homeland Security has repeatedly stressed in recent months that migrants apprehended under Title 8 authority may face a swift deportation process, known as “expedited removal” – and a ban on reentry for at least five years. Those who make subsequent attempts to enter the US could face criminal prosecution, DHS has said.

But the processing time for Title 8 can be lengthy, posing a steep challenge for authorities facing a high number of border arrests. By comparison, the processing time under Title 42 hovered around 30 minutes because migrants could be quickly expelled, whereas under Title 8, the process can take over an hour.

Title 8 allows for migrants to seek asylum, which can be a lengthy and drawn out process that begins with what’s called a credible-fear screening by asylum officers before migrants’ cases progress through the immigration court system.

Title 8 has continued to be used alongside Title 42 since the latter’s introduction during the Covid-19 pandemic, with more than 1.15 million people apprehended at the southern border under Title 8 in fiscal year 2022, according to US Customs and Border Protection. More than 1.08 million people were expelled under Title 42 at the southern land border during that same period.

There’s also a new border policy

The administration is also rolling out new, strict policy measures following the lifting of Title 42 that will go into effect this week.

That includes putting into place a new asylum rule that will largely bar migrants who passed through another country from seeking asylum in the US. The rule, proposed earlier this year, will presume migrants are ineligible for asylum in the US if they didn’t first seek refuge in a country they transited through, like Mexico, on the way to the border. Migrants who secure an appointment through the CBP One app will be exempt, according to officials.

If migrants are found ineligible for asylum, they could be removed through the speedy deportation process, known as “expedited removal,” that would bar them from the US for five years.

Jose Luis Gonzalez/Reuters
Migrants cross the Rio Bravo to return to Ciudad Juárez, Mexico, on Saturday, May 13, as members of the Texas National Guard extend razor wire at the border.
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Alison, a 6-year-old migrant from Honduras, stands with her mother while they wait to be transported to a US Border Patrol processing facility in La Joya, Texas, on May 13.
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US Border Patrol agents watch over migrants waiting to take a bus to a processing center in Fronton, Texas, on Friday, May 12. The migrants had turned themselves in after crossing from Mexico.
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A group of men from El Salvador are detained by US Border Patrol agents after crossing the border near Sunland Park, New Mexico, on May 12.
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Migrants waiting to apply for asylum near San Diego reach through a border wall for clothing handed out by volunteers on May 12.
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A US Border Patrol agent searches a man from Mexico who crossed the border illegally near Sunland Park on May 12.
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Ligia Garcia and her husband, Robert Castellon, walk with their children to buy food after they were processed by US border officials in McAllen, Texas, on May 12.
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Paula, a woman from Guatemala, holds her daughter as she asks US border officials about the new asylum rules at the San Ysidro Port of Entry, between San Diego and Tijuana, Mexico, on Thursday, May 11.
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Migrants in Matamoros, Mexico, gather on the banks of the Rio Grande as they get ready to cross the border to turn themselves in on May 11.
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Merejido Del Orbe, who came to the United States from the Dominican Republic, rests at Annunciation House, a shelter in El Paso, Texas, on May 11. He broke his leg when he slipped from a rope while climbing a border fence in April.
Daniel Becerril/Reuters
Texas National Guard soldiers place more razor wire on the banks of the Rio Grande in Matamoros on May 11.
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Migrants from Peru react after crossing the border in Yuma, Arizona, just a few minutes before the lifting of Title 42 on May 11.
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As the sun sets on May 11, migrants wait to be processed by US Border Patrol agents across the border from El Paso.
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Migrants released by US border officials are seen at a cell phone charging station at the Regional Center for Border Health in Somerton, Arizona, on May 11.
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Migrants surrender to the US Border Patrol in Yuma on May 11.
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Erick Torres and his son Benjamin, migrants from Peru, wait to be processed by US Border Patrol agents in Yuma on May 11.
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Migrants climb onto an air mattress in Matamoros to prepare to cross the Rio Grande toward Brownsville, Texas, on May 11.
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Migrants board a bus after surrendering to US Border Patrol agents in Yuma on May 11.
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A US Border Patrol agent looks on as migrants wait to apply for asylum near San Diego on May 11.
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Norma Garcia Bonilla, from Michoacán, Mexico, waits at Albergue del Desierto, a migrant shelter in Mexicali, Mexico, across from the California border, on Wednesday, May 10. She is seeking asylum in the United States.
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Hundreds of migrants in Ciudad Juárez wait to cross into the United States on May 10.
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Migrants carry a baby in a suitcase across the Rio Grande on May 10.
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A migrant tears up behind a border wall near San Diego on May 10.
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Members of the Texas National Guard are deployed to an area of high migrant crossings in Brownsville on May 10.
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Wendy Velasquez and her 21-month-old daughter, Starley Dominguez Velasquez, have been living for five months at the Albergue del Desierto migrant shelter in Mexicali. They came from Honduras to apply for asylum in the United States.
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Migrants wait to get paid after washing cars at a gas station in Brownsville on May 10. They had arrived the day before from Mexico.
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Migrants surrender to US Border Patrol agents after crossing the border in Yuma on May 10.
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Migrants cross the Rio Grande from Matamoros on May 10.
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Migrants gather between primary and secondary border fences near San Diego on May 10.
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Migrants stand in line as they wait to be processed by US Border Patrol agents in Brownsville on May 10.
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A migrant climbs over a border wall separating Tijuana from the United States after fetching groceries for other migrants who were waiting to be processed by US authorities on May 10.
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A heart-shaped keychain with a photo of Salvadoran migrant Danilo Ruiz and his family hangs from a handbag at a makeshift shelter in Reynosa, Mexico, on Tuesday, May 9.
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Migrant families cross into El Paso from Mexico on May 8.
Mike Blake/Reuters
A US Border Patrol agent watches over migrants who had gathered in San Diego on May 8.
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A woman is helped off a freight train after she became too scared to climb down from the roof on May 7. Migrants have been traveling on top of freight trains as they headed north from southern Mexico. The woman's son, Leonardo Luzardo, told CNN it had been a long, cold night atop the train, feeling like their bodies were turning to ice. "It seemed like we were going to freeze," he said.
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Migrants who were trying to evade US Border Patrol agents wait to be processed in Granjeno, Texas, on May 4.
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Children play soccer at a shelter in Tijuana on May 3. Their families were awaiting the end of Title 42.
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Migrants camp out in an alley behind the Sacred Heart Church in downtown El Paso on April 30.
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Migrants wait to be processed by US Border Patrol agents in Santa Teresa, New Mexico, on April 26.

The administration also plans to return Cubans, Venezuelans, Haitians and Nicaraguans to Mexico if they cross the border unlawfully, marking the first time the US has sent non-Mexican nationals back across the border.

The new asylum rule is already facing a legal challenge as the ACLU and other immigrant advocacy groups filed a lawsuit overnight Thursday in an effort to block the policy.

“The Biden administration’s new ban places vulnerable asylum seekers in grave danger and violates U.S. asylum laws. We’ve been down this road before with Trump,” said Katrina Eiland, managing attorney with the ACLU Immigrants’ Rights Project, in a statement. “The asylum bans were cruel and illegal then, and nothing has changed now.”

Senior administration officials have stressed the actions are necessary to encourage people to use lawful pathways to come to the US. That includes parole programs for eligible nationalities to apply to enter the US and expanding access to an app for migrants to make an appointment to present themselves at a port of entry.

The advocates’ lawsuit, filed in federal court in the Northern District of California, cites issues with the CBP One app used for scheduling asylum appointments, including some migrants’ lack of resources to get a smartphone and the absence of adequate internet access to use the app, along with language and literacy barriers.

The State Department plans to open about 100 regional processing centers in the Western hemisphere where migrants can apply to come to the US, though the timeline for those is unclear.

“We have, however, coupled this with a robust set of consequences for noncitizens who, despite having these options available to them, continue to cross unlawfully at the border,” a senior administration official told reporters Tuesday.