Joe Biden can quickly reverse many of Donald Trump’s immigration policies, experts say. Others will be more complicated.

It took less than a half hour after the presidential election was called for President-elect Joe Biden on Saturday before Krish O’Mara Vignarajah tweeted her thoughts on what she expected from the incoming administration.

“We will, day-in and day-out, hold the Biden administration accountable to its promises to immigrants, refugees, DREAMers, and the American people,” she wrote. “And together, we can and we will build a fair and humane immigration system that reflects our better angels.”

As the president and CEO of Lutheran Immigration and Refugee Service, Vignarajah was one of several immigrant rights leaders who decried President Donald Trump’s decision last month to cut the annual refugee limit to 15,000, the lowest ceiling in the history of the 40-year-old resettlement program — down from 30,000 in 2019 and 45,000 in 2018.

The refugee limit was the latest in a four-year string of hard-line actions by the Trump administration to curb legal and unauthorized immigration to the United States, one of the areas where Trump has had more successes than failures in delivering on his campaign promises.

With the election decided — although Trump has not conceded and his campaign has filed lawsuits in multiple states to contest the results — how quickly a Biden administration can begin to reverse course on Trump’s immigration policies depends on several factors. They include how far-reaching the policies are, what Biden can accomplish via executive order and whether Congress has an appetite to take on such measures amid other priorities like the ongoing COVID-19 pandemic and the country’s economic recession.

Sarah Pierce, an analyst at the Migration Policy Institute, a Washington, D.C.-based policy think tank, said one of the issues Biden can tackle quickly is also one of the most popular and controversial: the Obama-era Deferred Action for Childhood Arrivals program.

The 2012 program provided renewable, two-year work permits and a reprieve from deportation to hundreds of thousands of immigrants who were brought into the U.S. as children; it was open to undocumented immigrants who came to the country before they were 16 and who were 30 or younger as of June 2012. Roughly 107,000 Texans had DACA permits as of December 2019, according to federal statistics.

Trump announced in 2017 he was ending the program, but the U.S. Supreme Court ruled in June that was inappropriately terminated.

“Reinstating DACA to its full force would likely only require a memo,” Pierce said. “And it would mean opening [the program] up to more than 400,000 young foreign nationals who are immediately eligible for DACA benefits but unable to apply.”

A Trump administration policy that’s had a big impact on the border, the Migrant Protection Protocols, might not be as easy to eliminate, Pierce said. The policy, known as “remain in Mexico,” was enacted in late 2018 in California and a few months later in the El Paso-Ciudad Juárez region before expanding to other major population centers along the Texas-Mexico border.

The Migrant Protection Protocols require that most asylum seekers wait in Mexico for their court dates in front of American immigration judges. More than 67,000 asylum seekers have been sent back to Mexico, including more than 20,000 in the El Paso-Ciudad Juárez area, since the program’s inception.

“Procedurally that would likely require little more than a policy memo — that is actually how it was created,” Pierce said. “But there will be a lot of questions about what to do with the … individuals who are currently or were previously enrolled in MPP. Those questions will present a lot of political and logistical difficulties for the new administration.”

The Mexican government would likely be included in those discussions, but Mexican President Andrés Manuel López Obrador is one of the few world leaders who has not congratulated Biden. Instead, López Obrador — or AMLO, as he’s commonly referred to — said he was going to wait until any legal disputes over the U.S. election were resolved.

Duncan Wood, the director of the Mexico Institute at the Washington, D.C.-based Wilson Center, said López Obrador’s decision to wait was somewhat surprising but won’t be a major diplomatic issue once the election results are finalized.

“It sends the message that the president himself isn’t interested and isn’t excited about working with a new president of the U.S.,” Wood said. “But it’s unlikely to have long-term ramifications just because of the nature of the relationship.”

In 2019, Trump threatened to shut down the southern border if Mexico didn’t do more to stop caravans of migrants from Central America from traveling through Mexico en route to the United States. López Obrador responded to the threats by sending federal troops to his country’s northern border to prevent the migrants from entering the United States and by keeping asylum seekers in makeshift encampments south of the Rio Grande.

Wood said he expected a Biden administration to take a more traditional approach with Mexico that includes dialogue and offers of U.S. aid.

“It’s going to be very difficult for a Biden administration to relax or to end the cooperation with Mexico on stopping the flow of Central Americans northward,” he said.

On construction of the border wall, which Trump made a signature issue of his 2016 campaign, Biden can immediately end Trump’s 2019 emergency declaration that allowed him to transfer billions in Department of Defense construction and payroll funds to finance the border barrier. But it’s unclear what would become of the funds that were transferred but haven’t been used, said Jessica Bolter, a Migration Policy Institute policy analyst.

“Ending the transfer of future funds doesn’t mean in itself that wall construction stops,” she said. “If Biden wants to follow through with his promise not to build another foot of wall, his administration could [also] terminate current contracts for wall construction, possibly even if they’re in the middle of construction, which the government does have a lot of leeway to do.”

There are also pending federal lawsuits in Texas about the Trump administration’s use of eminent domain to acquire private land to build more miles of barrier. The litigation has stalled construction so far in Webb and Zapata counties. But those lawsuits would be a moot point if Biden decides to stop new construction altogether.

The president-elect has also promised to send to the next Congress a bill to provide a path toward legal status for the millions of undocumented immigrants in the United States. But addressing the ongoing pandemic and the economic recession it has caused will likely be a bigger immediate priority, said Muzaffar Chishti, a senior fellow at the MPI.

“That makes, I think, real progress on some other important issues very difficult for the immediate future,” Chishti said.