President-elect Trump is returning to the White House looking to dwarf his first term’s significant impact on immigration policy.

Eight years after he first won the presidency, Trump has remolded the GOP’s mainstream views on immigration, all but guaranteeing he will face less resistance in implementing his more extreme proposals.

But questions remain about the capacity of a new Trump administration — or of immigration enforcement agencies — to run a deportation program that lives up to his campaign promises.

Still, Trump’s first term brought deep behind-the-scenes changes to the immigration and border security systems, changes that took the Biden administration months to undo in some cases.

Trump’s new team is likely to quickly reinstate those policies, looking to pick up where they left off in 2021.

Border security

Trump left President Biden a border with relatively few unauthorized migrant encounters per month but primed to explode with tens of thousands or hundreds of thousands of people bottlenecked south of the U.S.-Mexico line.

That bottleneck was exacerbated by quick expulsion policies such as Title 42, a measure Biden kept in place until 2023, drawing the ire of many in the immigration advocacy movement.

Title 42 and the Migrant Protection Protocols, also known as “Remain in Mexico,” were stalwarts of the Trump administration’s attempts to curb border crossings that Republicans routinely used as a cudgel to blame the Biden administration for the massive growth in unauthorized arrivals.

Those arrivals peaked with more than 300,000 migrant encounters last December.

Comparatively, there were nearly 74,000 encounters in December of 2020, Trump’s last full month in office, with Title 42 and Remain in Mexico in place, including 71,141 encounters between ports of entry.

In September of 2024, Customs and Border Protection (CBP) reported 101,790 encounters at the southwest border, 53,858 of which were reported by the Border Patrol between ports of entry.

That suggests the border under Trump was in some ways more porous than under Biden, with a broad majority of migrants evading ports of entry to turn themselves over to the Border Patrol.

Biden ran a carrot-and-stick approach to border enforcement. The carrot — stay in line for a shot at legal entry into the United States — attracted migrants to CBP-run ports of entry.

The sticks — Biden’s draconian interpretation of asylum law and offshoring of immigration enforcement duties to Mexico — helped move the bottlenecks south, potentially at the expense of human rights violations within Mexico, and provided further incentive for migrants to line up for the Biden administration’s parole programs.

The incoming administration may keep the sticks, but it will almost certainly do away with the carrot, potentially ramping up the Border Patrol’s workload.

Mass deportations

Trump’s pledge to create the largest deportation force in U.S. history has taken center stage in the transition period, with incoming border czar Tom Homan making frequent media appearances to tout the policy.

Immigrant advocates have warned communities to take the threats seriously, while at the same time expressing skepticism that the new administration will overcome the hefty logistical, budgetary and legal limitations.

Those limitations, however, are difficult to define because much of the current deportation system operates in the shadows.

The American Civil Liberties Union (ACLU) on Monday launched a public records suit against U.S. Immigration and Customs Enforcement (ICE) seeking information about ICE Air, the government’s method for carrying out deportation flights.

While the suit would gain records about how the airline was used to carry out some 140,000 deportations in 2023 under the Biden administration, the ACLU is also eager to understand whether the network of private charter flights could be expanded.

“For months, the ACLU has been preparing for the possibility of a mass detention and deportation program, and FOIA litigation has been a central part of our roadmap,” Kyle Virgien, senior staff attorney at the ACLU’s National Prison Project, said in a statement.

But Trump has made clear he wants to activate new powers to carry out his goals.

He confirmed Monday that he would declare an immigration national emergency and use military assets to support his mass deportation pledge

Numerous Republican governors have, under the Biden administration, already sent their National Guards to the border, though such units are not deputized to carry out any immigration enforcement roles.

It’s also not clear the extent Trump will have buy-in from border state governors, several of whom are Democrats.

Arizona Gov. Katie Hobbs (D) said that while she would continue ongoing partnerships with the federal government and advocate for border needs, that there are Arizonans who “are worried about threats from the Trump administration as well.”

“I will not tolerate terrorizing communities, or threatening Arizonans,” she said.

Rep.-elect Emily Randall (D-Wash.) expressed concern the Trump administration might try to “pull funding” from states that don’t cooperate with his immigration plans.

“I think we don’t know what it looks like in our communities. We don’t know the logistics of what is going to happen, but we know that there’s going to be increased pressure. And you know, as a former legislator, I’m worried about what kind of economic leverage the Trump administration is planning to use on states like Washington,” she said.

“I’ve heard talk about withholding federal funding for sanctuary states, states where we don’t plan to be complicit in mass deportations.”

Who would be targeted?

While past administrations have largely focused on more recent arrivals as well as those who pose a public safety threat, Trump has made clear that anyone who is undocumented could face removals.

It’s a large group, an estimated 12 million people, and one the government has traditionally indicated it simply doesn’t have the resources to prioritize.

Many have been living, working and paying taxes in the U.S. for decades.

Trump’s hardline immigration stance has also unnerved those who currently have work authorization under DACA, the Obama-era Deferred Action for Childhood Arrivals program, which provides protection for those brought to the U.S. as children but which has never been formally approved by Congress.

Incoming deputy White House chief of staff Stephen Miller has also said the administration will turn its efforts toward naturalized citizens, expanding the federal government’s oversight of past naturalizations.

Denaturalizations are fairly uncommon, and legal precedent is clear that only naturalized citizens who lied in their applications in a material way — about something that directly affected their eligibility for naturalization — are subject to legal review of their citizenship papers.

Rep. Adriano Espaillat (D-N.Y.), a naturalized Dominican-born U.S. citizen, said he will oppose any efforts to pursue denaturalizations.

“I think it’s a radical approach, one that is unprecedented in America, and I think that the vast majority of American people will oppose it as well,” said Espaillat, who is running unopposed to lead the Congressional Hispanic Caucus in the next Congress.

Still, the first Trump administration successfully re-tooled United States Citizenship and Immigration Services — the agency in charge of processing work permits, permanent residence and naturalizations — from an organization focused on providing services to applicants to one with a greater focus on reviewing past applications for indications of fraud.

Advocates fear that wide net, stretching from undocumented workers to naturalized citizens and from the border to sanctuary jurisdictions, will further stigmatize immigrants and prove disruptive to the communities that surround them.

“I expect to be flooded with calls and visits to my district office with immigrants and families or mixed-status families asking for help and being scared [about] what this means for them, and I hope to bring back the resources and that protection,” said Rep.-elect Luz Rivas (D-Calif.), whose district includes San Fernando, a city where more than 35 percent of residents were born abroad.

“You know, my hope is that they don’t — the community doesn’t stop going to the hospital when they need to, doesn’t stop sending their children to school. So I will be working along with local leaders in Los Angeles, like our mayor, our city council members, our state legislators, to send out a unified message to the community.”