If re-elected president, Donald Trump has promised mass deportations of those who do not have legal permission to be in the United States.
While his campaign has offered varying answers about how many might be removed, his vice presidential candidate J.D. Vance provided a figure during an interview with ABC News this week.
“Let’s start with a million,” he said. “That’s where Kamala Harris failed. And then we can go from there.”
But while it has been a key pillar of Trump’s platform — with signs at his rallies reading “Mass Deportations Now!” — experts say there are significant legal and practical challenges to deporting so many people.
What are the legal challenges?
The latest data from the Department of Homeland Security and the Pew Research Center indicate that there are currently approximately 11 million undocumented immigrants living in the United States, a number that has remained relatively stable since 2005.
Most of them are long-term residents: about four-fifths have been in the country for more than a decade.
Immigrants who are in the country without legal status are entitled to due process, including a court hearing before their deportation. A dramatic increase in deportations would likely require a major expansion of the immigration court system, which has been plagued by backlogs.
Most immigrants already in the country enter the deportation system not through encounters with Immigration and Customs Enforcement (ICE) agents, but through local law enforcement.
However, many of the country’s largest cities and counties have passed laws limiting local police cooperation with ICE.
The Trump campaign has pledged to take action against these “sanctuary cities,” but America’s patchwork of local, state, and federal laws further complicates the picture.
Kathleen Bush-Joseph, a policy analyst at the Washington-based Migration Policy Institute (MPI), said that cooperation between ICE and local officials would be an “essential” aspect of any mass deportation program.
“It’s much easier for Ice to get someone out of jail if local law enforcement cooperates, rather than having to go out and look for them,” he said.
As an example, Ms. Bush-Joseph cited a statement released in early August by the sheriff’s offices of Broward and Palm Beach counties in Florida, saying they would not send officers to support any mass deportation plan.
“There are many others who would not cooperate with a Trump mass deportation plan,” he said. “That makes it much more difficult.”
Any mass deportation program is likely to be met almost immediately with a flurry of legal challenges from immigration and human rights activists.
However, a 2022 Supreme Court ruling says courts cannot issue injunctions on immigration enforcement policies, meaning they would remain in place even as challenges work their way through the legal system.
But is it logistically possible to do this?
If a U.S. administration were able to legally proceed with plans for mass deportations, authorities would still face enormous logistical challenges.
During the Biden administration, deportation efforts have focused on migrants recently detained at the border. Migrants deported from deeper within the United States, from areas not near the border, are overwhelmingly those with criminal records or considered national security threats.
Controversial construction site raids carried out during the Trump administration were suspended in 2021.
Deportations of people apprehended inside the United States, as opposed to those at the border, have remained below 100,000 for a decade, after peaking at more than 230,000 during the early years of the Obama administration.
“To get to a million in a single year would require a huge injection of resources that probably don’t exist,” Aaron Reichlin-Melnick, policy director of the American Immigration Council, told the BBC.
First, experts doubt that ICE’s 20,000 agents and support staff are enough to find and track even a fraction of the numbers touted by the Trump campaign.
Mr Reichlin-Melnick added that the deportation process is long and complicated and begins only with the identification and arrest of the illegal migrant.
After that, detainees will have to be housed or placed in an “alternative to detention” program before being brought before an immigration judge, in a system that is backlogged for years.
Only then are the detainees expelled from the United States, a process that requires diplomatic cooperation from the receiving country.
“In each of these areas, Ice simply does not have the capacity to handle millions of people,” Reichlin-Melnick said.
Trump said he would engage the National Guard or other U.S. military forces to facilitate deportations.
Historically, the U.S. military’s role in immigration matters has been limited to support functions at the U.S.-Mexico border.
Aside from using the military and “using local law enforcement,” Trump has provided few details on how such a mass deportation plan might be implemented.
In an interview with Time magazine earlier this year, the former president said only that he “would not rule out” building new migrant detention centers and that he would move to grant police immunity from prosecution by “liberal or progressive groups.”
He added that there may also be incentives for state and local police departments to participate, and that those who don’t “won’t share in the riches.”
“We have to do this,” he said. “This is not a sustainable problem for our country.”
The BBC has contacted the Trump campaign for further comment.
Eric Ruark, research director at NumbersUSA, an organization that advocates for tougher immigration controls, said any internal deportation program would only be effective if coupled with increased border enforcement.
“That has to be the priority. If it’s not, there’s going to be very little progress going forward internally,” he said. “That’s what keeps people coming.”
Mr Ruark also said that tough measures should also be taken against companies that hire illegal migrants.
“They come for the jobs,” he said. “And they get them because domestic law enforcement has been essentially dismantled.”
The financial and political costs
Experts estimate that the overall cost of a million or more deportations would amount to tens or even hundreds of billions of dollars.
ICE’s transportation and deportation budget for 2023 was $420 million (£327 million). That year, the agency deported just over 140,000 people.
Thousands of immigrants would be held awaiting court hearings or deportations, and Trump’s campaign has called for the construction of large encampments to house them all.
The number of ejection flights would also need to be significantly increased, which may require the use of military aircraft to augment current capacity.
Even a small expansion in any of these areas could result in significant costs.
“Even a small change is in the tens of millions, or hundreds of millions,” Mr. Reichlin-Melnick said. “A significant change is in the tens or hundreds of millions.”
Those costs would come on top of spending on other border control efforts Trump has promised: continued work on a wall on the southern U.S. border, a naval blockade to prevent fentanyl from entering the country, and the movement of thousands of troops to the border.
Adam Isacson, a migration and border expert at the Washington Office on Latin America, said the “nightmarish images” of mass deportations could also have a political cost from a public relations standpoint for a possible Trump administration.
“Every community in the United States would see people they know and love riding buses,” Isacson said.
“There would be some very painful images on TV of crying children and families,” he added. “This is all very bad publicity. It’s family separation, but on steroids.”
Have mass deportations occurred in the past?
In the four years of the previous Trump administration, approximately 1.5 million people were deported, both from the border and from within the United States.
Statistics show that the Biden administration, which had deported about 1.1 million people through February 2024, is on track to match that figure.
During the two terms of the Obama administration, when Biden was vice president, more than three million people were deported, prompting some immigration reform advocates to dub Barack Obama “deporter-in-chief.”
The only historical comparison to a mass deportation program was in 1954, when approximately 1.3 million people were deported under Operation Wetback, named after a derogatory slur then commonly used against Mexicans.
This figure is, however, disputed by historians.
The program, under President Dwight Eisenhower, encountered considerable public opposition, partly because some U.S. citizens were also deported, as well as a lack of funding. It was largely discontinued by 1955.
Immigration experts say the focus on Mexican citizens and the lack of due process during the previous operation make it incomparable to a modern mass deportation program.
“Those [deported in the 1950s] “They were single Mexican men,” said MPI’s Kathleen Bush-Joseph.
“Now, the vast majority of people moving between ports of entry are coming from places other than Mexico, or even northern Central America. That makes it much more difficult to repatriate them,” he added.
“Those are not comparable situations.”