President-elect Donald Trump confirmed Monday that he intended to declare a national emergency and use the U.S. military in some form to assist in his plans for mass deportations of immigrants who do not have legal residency status.

On his social media platform, Truth Social, Trump responded overnight to a post made this month by Tom Fitton, who runs the conservative group Judicial Watch and who wrote that Trump’s administration would “declare a national emergency and will use military assets” to address illegal immigration “through a mass deportation program.”

Around 4 a.m., Trump reposted Fitton’s post with the comment, “TRUE!!!”

Congress has granted presidents broad power to declare national emergencies at their discretion, unlocking standby powers that include redirecting funds lawmakers had appropriated for other purposes. During his first term, for example, Trump invoked this power to spend more on a border wall than Congress had been willing to authorize.In interviews with the New York Times during the Republican primary campaign, described in an article published in November 2023, Trump’s top immigration policy adviser, Stephen Miller, said that military funds would be used to build “vast holding facilities that would function as staging centers” for immigrants as their cases progressed.

The Homeland Security Department would run the facilities, he said.

One major impediment to the vast deportation operation that the Trump team has promised in his second term is that Immigration and Customs Enforcement, or ICE, lacks the space to hold a significantly larger number of detainees.

That has sometimes led to allowing asylum-seekers into the country while they await court dates with immigration judges, a practice critics deride as “catch and release.”

The Trump team believes that such camps could enable the government to accelerate deportations of immigrants who fight their expulsion from the country. The idea is that more people would voluntarily accept removal instead of pursuing a long-shot effort to remain in the country if they had to stay locked up in the interim.

Asked about the proposal, Sabrina Singh, a spokesperson for the Pentagon, declined to comment, calling it “a hypothetical.”

Immigrant advocates assailed the move, raising alarms about potential fallout.

“President-elect Trump’s dystopian fantasies should send a chill down everyone’s spine, whether immigrant or native-born,” said Karen Tumlin, director of the Justice Action Center, an immigrant advocacy organization.

Congressional Democrats responded with a similar level of incredulity, asserting that such a move was all but certain to violate federal laws preventing the use of the military on U.S. soil.

“We’re pursuing whatever we can do to make clear that the Insurrection Act should not permit that use of the military,” said Sen. Richard Blumenthal, D-Conn., referring to the 1807 law that grants presidents emergency power to use troops on domestic soil to restore order when they decide a situation warrants it. Under that law, “if there is no threat to public order of a fundamental, far-reaching kind, it would be illegal,” he added.

Republicans, however, suggested that Trump’s proposal might not be a radical departure from the status quo.

“Obviously they’re not law enforcement, but I have to see what their process is,” said Sen. James Lankford, R-Okla., who served as the lead Republican negotiator on a bipartisan immigration deal that failed to pass the Senate after Trump urged the GOP to reject it. “If the National Guard is providing transportation, they do that a lot already.”

Miller has also talked about invoking a public health emergency power to curtail hearing asylum claims, as the Trump administration did during COVID-19.

Trump’s declaration of a national emergency at the southern border amid a surge in asylum-seekers and his reprogramming of military funds toward his border wall in 2019 was a face-saving way out of a spending standoff with Congress that had led to a government shutdown. It led to legal challenges that had not been resolved before President Joe Biden took over and halted further construction on the border wall.

Other elements of the team’s plan include bolstering the ranks of ICE officers with law enforcement officials from other agencies, and with state National Guard members and federal troops activated under the Insurrection Act.

The team also plans to expand a form of due-process-free expulsions known as expedited removal, which is currently used near the border for recent arrivals, to people living across the interior of the country who cannot prove they have been in the United States for more than two years.

And the team plans to stop issuing citizenship-affirming documents, like passports and Social Security cards, to infants born on domestic soil to migrant parents who are not legal residents in a bid to end birthright citizenship.