The first wave of U.S. troops has moved to the southern border to “repel an invasion” of immigrants, as the Trump administration puts it.
The U.S. military is also preparing U.S. bases to hold people rounded up as part of President Donald Trump’s mass deportation plan, and is conducting flights to remove them from the country.
One such base will be in Guantánamo Bay, Cuba, Mr. Trump announced Wednesday. His order is to use the detention facility to begin receiving 30,000 “criminal aliens.”
Why We Wrote This
President Donald Trump’s push to involve the U.S. military with border security and use Guantánamo Bay to hold migrants is part of his strategy to test the limits on use of the armed forces.
The president has “made it very clear there’s an emergency at the southern border,” Defense Secretary Pete Hegseth said upon his arrival at the Pentagon Monday, in his first remarks on the job. And the cartels who are moving drugs across it “are foreign terrorist organizations,” he added.
These words – invasion, emergency, terrorist organizations – have legal meanings that give the president particular powers to mobilize the U.S. military. Precisely what the Trump administration asks troops to do as part of the mass deportation now underway is something American legal scholars are closely tracking.
Why hold migrants in Guantánamo Bay?
President Trump said in a memo Wednesday that it is a move to “halt the border invasion, dismantle criminal cartels, and restore national sovereignty.”
Secretary Hegseth called “Gitmo,” a nickname for the base, “the perfect location” in a statement on the social platform X. The Department of Defense would “immediately” expand the detention center to full capacity, he added.
U.S. law allows for the use of military bases for state and federal law enforcement. Human rights analysts argue, however, that moving such operations to Guantánamo Bay raises legal concerns.
Migrants held there would face barriers to accessing due process rights like access to lawyers, they say. There is also the matter of how long these people would stay there, a basic tenet of habeas corpus. Many of the roughly 800 prisoners held at Gitmo during the height of the war on terror faced indefinite detention. A quarter century later, there are 15 people left in cells, some still awaiting trial.
Mr. Hegseth has said that the plan is to provide “temporary transit” in a separate area of the U.S. Navy base, which includes a golf course and has been used for disaster operations in the past.
Critics voiced concern that the administration is nonetheless using Guantánamo because it’s “a legal black hole,” as the National Immigration Law Center put it in a statement this week. “It’s a stain on our nation’s history and has no business being used for detaining migrants or anyone else.”
What are the legal constraints for U.S. troops operating on American soil?
The active duty military can support law enforcement, but it cannot act as domestic police or take part in arrests or search and seizures, for example. This is at the heart of the longstanding Posse Comitatus Act of 1878.
U.S. Marine Corps/Sgt. Kyle Chan/Reuters
There are exceptions to it. If the president invokes the Insurrection Act, it temporarily suspends Posse Comitatus and allows him to federalize the National Guard and deploy active duty troops to suppress any uprising that interferes with the execution of state or federal law.
Scholars have called the 1807 act “dangerously vague” and “ripe for abuse” because it isn’t very clear when it comes to the conditions under which it can be used.
Mr. Trump considered invoking the act in the summer of 2020, after widespread protests erupted following the killing of George Floyd by police, but military leaders reportedly talked him out of it. It was last used in 1992, during the Los Angeles riots that followed the beating of Rodney King, a Black man, by police officers. The Insurrection Act has never been invoked for immigration enforcement.
For now, Congress is asking questions about the authority under which the Defense Department is using military aircraft for deportation flights.
“Detaining people and putting them on the flights – that looks much more like domestic law enforcement activity to me,” says Cassandra Burke Robertson, a professor of law at Case Western Reserve University. “I can see [legal] arguments being made on either side, but I think it crosses the line.”
Does using U.S. troops to aid in mass deportation threaten national security?
The U.S. military’s Northern Command now has 30 days to come up with a plan for how to use the military to seal the borders and repel an invasion, as the executive order puts it.
If interpreted literally by the command – whose plan must specify how many troops will be needed, for how long, and to do what, precisely – that’s an “enormous task” that could involve upwards of 10,000 troops, says retired Col. Mark Cancian, a senior adviser at the Center for Strategic and International Studies.
To date, 1,500 troops have been sent to the southern border, a figure consistent with other deployments there by other presidents over the course of 15 years. In the meantime, forces from the 82nd Airborne Division’s Immediate Response Force – which was sent to Iraq after an Iranian-backed militia attack on the U.S. embassy, for example, and to Afghanistan after the Taliban regained control of the country – are prepared for possible orders.
Lawmakers, for their part, are asking how the administration plans to balance the diversion of more U.S. military forces to the border with current missions and emergencies that could crop up in the wider world.
The mobilization begs a larger question as well: Why deploy active duty forces in this way when National Guard and reserve troops are available?
“The message Trump is sending is, ‘I am taking action immediately,’” Mr. Cancian says. Reservists take time to call up. And the choice to use active duty military highlights the relish with which the new administration approaches legal challenges, practically daring the courts to block it, analysts say.
It points to “an exploration of just how far Mr. Trump’s executive power can be extended,” Professor Robertson says.
Secretary Hegseth has said that U.S. forces would operate “in compliance with the Constitution, with the laws of our land, and the directives of the commander in chief.”
The question, analysts say, is whether those parameters will run headlong into one another. “Most presidents don’t try to test the limits,” Professor Robertson adds. “I think the Trump administration is not trying to operate within those limits.”
