FILE PHOTO: Republican presidential nominee Donald Trump speaks during a visit at the frontier with Mexico in Hereford, Cochise County, Arizona, U.S. August 22, 2024. REUTERS/Go Nakamura/File Photo/File Photo
(Reuters) - President-elect Donald Trump has vowed to use the U.S. military to help deport millions of undocumented migrants, a plan that breaks from U.S. tradition against deploying troops domestically but which legal experts said would still be hard to successfully challenge in court.
Trump advisers have said they intend to use the military to build detention camps or to transport undocumented migrants out of the U.S., freeing border patrol and immigration agents for investigations and apprehensions.
Experts said the administration would have legal cover if the military is confined to support roles, particularly along the border with Mexico, without interacting with suspects.
"I think that it probably won't face a whole lot of successful challenges," said Ryan Burke, a professor of military and strategic studies at the U.S. Air Force Academy, speaking in his personal capacity. "There's too much ambiguity in these laws to point to something that says, hey, you absolutely cannot do this."
The 1878 Posse Comitatus Act bars the federal military from participating in domestic law enforcement. Congress has created exceptions that have allowed presidents to successfully use active-duty military in support roles for things like fighting the illegal drug trade, as well as during breakdowns of law and order.
Trump has not explained how he plans to deploy the military to deport migrants. In a post last week on Truth Social, he responded "TRUE!!" to another user's post saying his incoming administration would use "military assets" in a mass deportation effort.
"President Trump will marshal every federal and state power necessary to institute the largest deportation operation of illegal criminals, drug dealers, and human traffickers in American history," Trump-Vance transition spokeswoman Karoline Leavitt said in a statement on Monday.
Every president since Bill Clinton in the 1990s has sent National Guard or active-duty soldiers to the border in support roles, ranging from surveillance to training and fixing equipment.
Experts said the support role exceptions to the Posse Comitatus Act might also allow the military to build vast camps to hold those slated for removal. Stephen Miller, an immigration adviser to Trump, floated that proposal to the New York Times in November 2023.
Deporting a million undocumented migrants annually will require the government to increase its detention capacity 20-fold, according to a report by American Immigration Council, an immigrant advocacy group.
Michel Paradis, a former Department of Defense attorney, said the more the military is asked to do, the more opportunities there are for legal challenges, even against a support role. He said using the military to build a detention camp might give a governor grounds to sue, if funds for the camp were diverted from a project in that governor's state.
BREACH OF NORMS, HARD TO CHALLENGE
Trump told Time Magazine in April he would support a deportation plan using the National Guard, a reserve force that answers to both the president and state governors.
When under state control, National Guard troops are not subject to the Posse Comitatus Act, even when going beyond a support role and actively policing.
In 2020, the Trump administration used National Guard under state control in Washington, D.C., to respond to protests over the murder of George Floyd by police in Minnesota.
But governors could refuse. Rob Bonta, the Democratic attorney general from California, told Reuters it was "dangerous ground" to have National Guard from one state brought into another state.
"California certainly will not take that laying down, and we will certainly examine any existing protections that we have to address that," he said.
If state governors refuse to send their National Guard, Trump could invoke the Insurrection Act, another exception to the Posse Comitatus Act.
There are several conditions for invoking the Insurrection Act, which allows soldiers to enforce the law. It has been used 30 times in U.S. history, according to New York University's Brennan Center for Justice, a left-leaning public policy institute.
Trump could be invited by a governor to invoke the act, as former President George H.W. Bush was in 1992 in response to riots in Los Angeles.
Trump could also invoke it on his own if there has been a breakdown in law and order or it is needed to defend civil rights. It was invoked in 1871 to fight racial violence by the Ku Klux Klan after the Civil War and in the 1950s and 1960s to enforce school desegregation and protect civil rights marches.
Anyone interacting with the military under the Insurrection Act would have the same Constitutional protections they have against any law enforcement. Military members acting on U.S. soil have been criminally investigated for incidents including for the shooting death of an American teenager in Texas in 1997.
Laura Dickinson, a professor at the George Washington University Law School, said while it would be hard to argue conditions exist to invoke the Insurrection act, courts usually defer to a president on issues of national security.
"It would be, I would argue, a strong breach of our constitutional norms and our constitutional tradition, but it would be hard to challenge in court," she said.
(Reporting by Tom Hals in Wilmington, Delaware; Additional reporting by Nate Raymond in Boston; Editing by Noeleen Walder)
