Donald Trump has promised a 'mass deportation.' It would cost billions.

If he returns to the White House, Donald Trump has vowed to launch a “mass deportation” of at least 11 million immigrants living in the United States without authorization.

He made a similar promise during his first administration. It didn’t pan out after he hit logistical and legal obstacles.

This time, experts say, things may be different.

A second, more experienced Trump administration will know "how to effectively use an enormous bureaucracy to their advantage," said César García Hernández, an Ohio State University law professor and author of "Migrating to Prison: America’s Obsession with Locking Up Immigrants."

There will be fewer legal obstacles, too. Trump appointed hundreds of judges during his first term, reshaping the courts that previously slowed or stopped his attempts to ramp up immigration enforcement.

The ramp-up is doable if a second Trump administration takes a "steroid-infused, whole-of-government approach," said Mark Morgan, who served as acting commissioner of U.S. Customs and Border Protection under Trump.

"The priorities will stay the same: going after convicted criminals," Morgan said. "However, nobody is off limits."

And if Trump wins a second term, experts say, public opinion may be on his side to do things Americans objected to before, like separating immigrant parents from their children in order to prosecute the adults.

A new USA TODAY/Suffolk University poll found 45% of respondents support Trump’s mass deportation proposal and 49% oppose it, with 4% undecided. The poll of 1,000 likely voters, taken by landline and cellphone Oct. 14 to 18, has a margin of error of plus or minus 3.1 percentage points.

Trump hasn't released detailed plans for a mass deportation. But a USA TODAY review of interviews and speeches by Trump and his former advisers and administrators indicate he intends to:

• Use emergency and executive authorities to bypass existing law, which includes protections for immigrants.

• Activate provisions under a law from the 1700s called the Alien Enemies Act, which was used to detain people of Japanese, German and Italian descent in World War II.

• Rely on local and state police, especially in like-minded Republican districts, to find and arrest immigrants in the country without permission.

• Employ the U.S. military and National Guard in immigration enforcement.

• Redirect federal employees and resources to support the effort.

A mass deportation of 1 million people per year could cost $88 billion annually, according to the nonpartisan American Immigration Council. It would require an unprecedented ramp-up of law enforcement staffing, detention capacity, immigration courtrooms and flight capacity.

"If President Trump gets reelected, the border is going to be sealed; the military will be deployed; the National Guard will be activated and the illegals are going home," Stephen Miller, a former adviser and architect of Trump's previous immigration policies, told a conservative podcast host earlier this year.

Who would Trump deport?

Pew Research estimates there are 11 million immigrants in the United States without authorization. The vast majority don't have a criminal conviction, and their individual situations can vary dramatically, from the asylum-seekers who crossed the border, to people who flew in on a tourist visa and overstayed.

Among them are some 1.3 million immigrants who have already been issued removal orders but remain in the country, said Kathleen Bush-Joseph, policy analyst at the nonpartisan Migration Policy Institute.

“That’s partly due to a lack of Immigration and Customs Enforcement officers, a lack of airplane capacity and the fact that some countries won’t take people back,” she said.

People with existing removal orders could be targeted first, as could the hundreds of thousands of immigrants who are in jail on local or state criminal charges, said Steven Camarota, director of research for the Center for Immigration Studies.

"That is the low-hanging fruit," he said, "all the people who get picked up under Secure Communities," a program that connected, under the Obama administration, local law enforcement jurisdictions with the U.S. Immigration and Customs Enforcement database.

ICE reported that, in July, there were more than 660,000 noncitizens with criminal histories on its docket.

Of the 11 million more than half are people who came legally but overstayed their visas, according to the Center for Migration Studies. Others crossed the border illegally years ago. They may have married U.S. citizens and may also have U.S. citizen children – and could be eligible, at some point, for legal status.

There are also hundreds of thousands of beneficiaries of temporary programs that could disappear with the stroke of a presidential pen.

"On a practical level," García Hernández said, the Trump camp "seems intent on expanding the pool of people who they target for potential removal from the United States to millions of people, including people who have the federal government’s permission to be in the United States."

More than 860,000 people from 16 different countries, such as Afghanistan, Ukraine, Syria, Venezuela and Haiti, benefit from "temporary protected status," according to the National Immigration Forum. That program can be canceled by Homeland Security at any time.

Another 530,000 immigrants, who arrived as children when their parents crossed the border illegally, benefit from a temporary status called Deferred Action for Childhood Arrivals, or DACA, according to U.S. Citizenship and Immigration Services. Trump tried to abolish the program, which began under the Obama administration. But the Supreme Court, which was then more liberal, blocked him.

An additional 1.6 million asylum-seekers are awaiting hearings in their cases, according to the Transactional Records Access Clearinghouse at Syracuse University.

“These are not people who have snuck into the country," said Mario Russell, executive director of the Center for Migration Studies. "They are people who have been given permission to have their cases heard.”

'Dragnet operations': How the government would find immigrants to deport

The immediate challenge to a mass deportation would be identifying and locating the millions of immigrants, here without legal status, who aren't on the government's rosters. Trump has said state and local law enforcement officers could help federal authorities.

The federal government "can tap into the greater intelligence community to put together targeting packages," Morgan said. That effort would likely be led by the U.S. Customs and Border Protection's National Targeting Center. Homeland Security agencies including the FBI and U.S. Marshals could participate, he said.

"I think you will see NTC be the hub receiving intelligence from different agencies," Morgan said. "State and local are an integral part of that."

If that collaboration were to happen, Russell said he expects it would lead to “catastrophic civil rights violations” based on poor evidence, poor forensics and poor profiling.

The investigations would lead to knocks on doors at people’s homes and raids on workplaces, he said – "essentially dragnet operations."

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Do immigrants have the same rights as citizens?

Immigrants accused of being in the country illegally have constitutional rights. For example, the Supreme Court has repeatedly held that the government can’t deport people without giving them “due process,” or the opportunity to tell a court why they should legally be allowed to stay.

Immigrants here without authorization also have the same basic rights as other defendants in criminal proceedings, including the right to a lawyer, the right against unreasonable searches, the right to remain silent, and the right against cruel and unusual punishment.

“You can’t just take people off the street, put them in a jail, on an airplane and send them abroad,” said Charles Kuck, an immigration lawyer.

That’s not to say immigrants without authorization enjoy all the same rights in practice.

The Supreme Court has held that typical immigration court proceedings are civil rather than criminal, so detained immigrants facing potential deportation only have a right to a lawyer if they can pay for it.

Migrants apprehended within two weeks of entering the country and within 100 miles of the border generally can be deported without a court hearing or lawyer.

Emergency authorities can also waive some rights.

During the COVID-19 pandemic, Trump invoked a public health law from the 1940s known as Title 42. The emergency authority allowed both his and the Biden administration to quickly return migrants to Mexico or their home country, without giving them a chance to make a claim to stay. U.S. Customs and Border Protection reported more than 2.7 million migrant expulsions at the Southwest border between 2020 and 2023.

Ken Cuccinelli, who served as acting deputy secretary of the Department of Homeland Security under Trump and is a senior fellow at the Center for Renewing America, said immigrants with deportation orders have limited rights.

"When it comes to the deportation process, illegal aliens legally do not have the same rights that an American accused of a crime has," Cuccinelli said.

How would Trump detain people awaiting deportation?

To put the scale of an operation to deport 11 million people into context, there were 1.2 million prisoners held in all of the country's state and federal prisons in 2022, according to the federal Bureau of Justice Statistics.

Immigration detention has historically been done on a much smaller scale.

Congress currently appropriates funding enough for ICE to hold an average of 34,000 people in detention daily. ICE uses more than 190 facilities to detain immigrants in at least 40 states and U.S. territories, according to agency statistics.

Trump has said he wouldn't need large detention centers because the deportations would happen swiftly.

But many immigrants have a right to plead their case to stay, but there's already a backlog of 3.5 million cases in the immigration court system. It could take months or years to get a hearing.

Likewise, foreign governments must agree to accept deportees. Those negotiations can take time, or fail; some countries, including China and Venezuela, have in the past refused to take back their citizens.

The American Immigration Council estimates the country would have to maintain 1,000 new immigration courtrooms and expand ICE’s detention capacity 24-fold to house all the people awaiting hearings.

Old law, new application: The Alien Enemies Act

Trump said he would invoke the Alien Enemies Act of 1798 to hasten deportations. The Republican Party embraced Trump’s plan in its platform, citing the law to justify removing known or suspected immigrant gang members, drug dealers or cartel members under the premise that their presence amounts to an invasion by a foreign government.

The courts could reject giving the president what are arguably only war-time powers over migration. However, courts have sometimes refused to second-guess a presidential administration’s judgment about what constitutes an “invasion,” or held that presidents have the final say.

Katherine Ebright, a lawyer who studies war powers at the Brennan Center for Justice, said the Alien Enemies Act is based on identity as a foreign citizen, not conduct or legal status.

“It doesn’t matter as long as you have that birth heritage or citizenship of the so-called foreign belligerent,” Ebright said.

Trump has also promised to employ the military and National Guard in his effort. Both Democrat and Republican administrations have used the National Guard to support border enforcement missions, but it would take invoking the Insurrection Act to put soldiers to work rounding up immigrants nationwide, experts say.

There is another potential role for the military, said Morgan, in the logistics of detention. Military installations around the country could provide space for detaining immigrants, particularly nonviolent offenders and families, he said.

"We detain them in family residential centers with all the medical care and amenities, as we’re going through the removal process to remove them to their country as a family," Morgan said. "The military can help with those kinds of facilities."

A history of deportation efforts

Trump has frequently said he would model his deportation effort after an operation 70 years ago under President Dwight D. Eisenhower.

Eisenhower's 1954 effort targeted hundreds of thousands of Mexicans and people of Mexican descent. It relied heavily on state and local law enforcement and resulted in a dragnet that rounded up and expelled U.S. citizens along with migrants.

But no president has ever tallied more deportations than President Barack Obama, who at the peak in 2012 removed more than 407,000 people, according to Syracuse's Transactional Records Access Clearinghouse. In total, his eight-year administration logged more than 3.1 million ICE deportations.

Trump's highest year of deportations was 2019, when his administration deported more than 269,000 people, according to the same TRAC dataset.

Across all four years of Trump's administration, ICE recorded just under 932,000 deportations.

Contributing: Nick Penzenstadler, USA TODAY.

This article originally appeared on USA TODAY: Mass deportation more likely in a 2nd Trump term, but costly