Alarm raised over proposed military 'buffer zone' along US-Mexico border

Citing five U.S. officials familiar with the discussions, the Washington Post reported Wednesday that the proposal would allow the Pentagon to take control of land along the U.S.-Mexico border, initially in New Mexico. If successful, the military installation could be expanded along the border’s 60-foot “buffer zone” — also known as the Roosevelt Reservation — in Arizona and California, too.

Militarizing the buffer zone would mean migrants entering the U.S. would be, in effect, trespassing on a military base, theoretically allowing troops to hold them for border agents, despite federal law preventing active-duty soldiers from engaging in civilian law enforcement, the Post said.

The move would give U.S. troops their most direct role so far in President Donald Trump’s border crackdown, and could allow the Department of Defense budget to help pay for it, according to the Post. It could also result in harsher penalties, such as accelerated deportations, for migrants entering the U.S. illegally.

The Post said, if the buffer zone plan is approved, that land “would likely become a temporary annex of an existing military installation, probably (Fort) Huachuca” in Sierra Vista.

Angela Camara, spokeswoman for Fort Huachuca, directed the Arizona Daily Star to the Office of the Secretary of Defense for comment on the possibility. A spokesperson for the office wrote in a Thursday email, “We have nothing to announce at this time.”

The plan would be an escalation of the Trump administration’s use of the military at the U.S. border, including the now-suspended use of costly military aircraft for deportations and the deployment of more than 10,000 active-duty soldiers to the border region.

On March 15, the U.S. also launched a guided-missile Navy destroyer, the USS Gravely, to become part of the Department of Defense’s southern border mission, “contributing to a coordinated and robust response to combating maritime related terrorism, weapons proliferation, transnational crime, piracy, environmental destruction, and illegal seaborne immigration,” according to a news release from U.S. Northern Command.

Fort Huachuca has been hosting 500 active-duty soldiers from the 10th Mountain Division out of Fort Drum in New York since February, and more troops have since been transferred there from Fort Carson in Colorado.

Earlier this month, U.S. Northern Command established the headquarters of its joint border-security task force at Fort Huachuca to “tactically synchronize” Defense Department efforts to “secure and seal” the border, the agency said.

Legal concerns

The Roosevelt Reservation is the federal strip of land that stretches 60 feet north from the international border. It was created in 1907 by President Theodore Roosevelt for border security, and encompasses land in New Mexico, Arizona and California.

The Interior Department “technically” manages the Roosevelt Reservation, but it’s “reserved for border security purposes and is under full operational jurisdiction of U.S. Customs and Border Protection,” J. Elizabeth Peace, Interior spokeswoman, said in an email.

A CBP spokesman said the agency had no comment on the Post’s reporting.

The Trump administration’s expanded use of active-duty U.S. troops risks violating a federal law, the 1878 “Posse Comitatus Act,” that prohibits federal troops from participating in civilian law enforcement, except when explicitly authorized by law.

A defense official told the Post they were being careful with their wording for that reason: Troops would be “holding” migrants for civilian law enforcement to pick up; not “detaining” them for arrest, the Post said.

The Posse Comitatus Act generally prevents the president from using the military as a domestic police force, and it doesn’t apply to the Coast Guard or National Guard, according to a 2021 explainer by Joseph Nunn, national security counsel for the progressive Brennan Center for Justice. The law “embodies an American tradition that sees military interference in civilian affairs as a threat to both democracy and personal liberty,” he wrote.

The Pentagon is likely unenthusiastic about the proposal, which would transfer highly trained soldiers to roles outside their area of expertise, said Adam Isacson, director for defense oversight at research and advocacy group Washington Office on Latin America, or WOLA.

“They’re not trained for this,” he said. “Now they’re being asked to like, guard thirsty families in the desert? And if they do see someone making a run for it, and have watched enough Fox News and think these are dangerous cartel people, they might overreact and treat them like an enemy. Then you have the military shooting civilians on U.S. soil.”

There’s also the question of whether there’d be a meaningful distinction between soldiers simply “holding” versus “detaining” migrants, he said. In some remote areas of the border, migrants couldn’t be quickly transferred to Border Patrol custody.

“In practice, especially if you’re out in the middle of the desert, holding them for hours and hours, what will that mean?” he said.

One of Trump’s executive orders gave defense and homeland security officials 90 days to decide whether to invoke the Insurrection Act, which could open the door to the president having broader power to use the military, Isacson said. The military was last deployed under the Insurrection Act during the L.A. riots in 1992, he said.

Response from Arizona’s senators

In an email to the Star, the office of Arizona Democratic Sen. Ruben Gallego said although the senator welcomes additional resources to help secure the border, “this is simply an expensive and flashy photo op that fails to offer long-term solutions. The Senator is committed to working across the aisle to secure the border and develop a comprehensive and sustainable immigration system that serves the people of Arizona.”

Sen. Mark Kelly, an Arizona Democrat, said in a Friday email, “Troops can support in emergencies, but this seems to go far beyond that. It risks putting servicemembers in roles they aren’t trained for, undermining their readiness for their missions. With the Trump administration touting low border crossings, it’s hard to justify the cost and impact of such a massive operation. We need real, lasting border solutions.”

Tucson Republican Rep. Juan Ciscomani did not respond to the Star’s requests for comment.

Isacson pointed out that between border agents, National Guard and active-duty troops in the border region, there were four soldiers or agents for every one migrant arrival in the month of February.

In February, border agents apprehended 8,300 migrants between ports of entry on the southern border, a 94% decrease from February 2024, CBP said.

The possibility of more boots on the ground in fragile borderland environments is concerning for environmentalists, including Erick Meza, borderlands coordinator for the Sierra Club. But Meza said the proposal is so new, and the Trump administration so “unpredictable,” the plan could be thrown out next week.

“The Sierra Club is monitoring closely and figuring out what ways we can hear from and support the communities at the border,” he said. “If there is an arrival (of troops) we want to be sure we’re in direct communication with Department of Homeland Security and Department of Justice to advocate to lessen the impact on some of these remote areas in the wilderness.”

The Border Patrol’s Tucson Sector is already one of the most heavily surveilled areas in the country, Meza said, and today’s low levels of migrant arrivals makes the militarization plan seem like a “political stunt.”

“It’s just bringing more military at a time where it’s not that much needed,” he said. “It just seems like a waste of resources, and an unnecessary impact to the environment.”