Military expands role as Air Force, Navy take over southern border lands

In a dramatic escalation of military involvement in immigration enforcement, the U.S. Air Force and Navy are taking over vast new swathes of federal land along the southern border, under a directive from Defense Secretary Pete Hegseth. 

One 250-mile stretch, located in Texas’ Cameron and Hidalgo counties, is being transferred to Air Force control and will fall under the jurisdiction of Joint Base San Antonio and be managed as part of a newly established National Defense Area (NDA).

The land is being transferred from the International Boundary and Water Commission, an agency traditionally responsible for handling water and boundary disputes between the U.S. and Mexico, marking a significant shift in the use and oversight of federal land at the border.

Another 140-mile stretch of land along the border near Yuma, Arizona, will be transferred to Navy jurisdiction.

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These mark the third NDAs created under the Trump administration, following similar moves in New Mexico and near El Paso, Texas. The areas are designated as military zones to bolster border security operations amid a surge in illegal crossings under the Biden administration. 

Troops authorized to detain migrants — a policy breakthrough

Presidents since Richard Nixon have deployed active-duty troops and reservists to the border. But until Trump, they’ve largely been restricted to logistical support: surveillance, building roads, etc. U.S. troops stationed in the NDAs will now be authorized to apprehend, search and detain migrants until Customs and Border Protection agents arrive. Migrants entering these zones may also face trespassing charges for entering military property.

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The move is part of a broader mission managed by the Joint Task Force – Southern Border (JTF-SB), a joint effort between the Air Force and U.S. Northern Command to consolidate and strengthen military presence along the border.

To support these efforts, the military has deployed Stryker vehicles, ground-based radar systems, and even begun 3D-printing drones to enhance surveillance capacity and reduce costs.

Pentagon spokesperson Sean Parnell said the coordinated efforts between DoD and Customs and Border Patrol led to zero “gotaways,” or migrants that escape authorities, across the entire southern border from June 28-30.

Legal and civil liberties concerns mount

Civil liberties groups have sounded the alarm, warning the policy blurs the lines between military and law enforcement roles and may violate the Posse Comitatus Act, which prohibits the use of federal troops in domestic policing without congressional approval.

“Using the military purpose doctrine to justify direct military involvement in immigration enforcement is a transparent ruse to evade the Posse Comitatus Act,” the Brennan Center for Justice said in a statement. “The nominal justification is protecting the installation, but the installation itself was created to apprehend and detain migrants.”

Critics also warn the policy could set a dangerous precedent. “If soldiers are allowed to take on domestic policing roles at the border, it may become easier to justify military deployments within the U.S. interior,” the Center added.

Andy Gould, former Arizona supreme court justice, said he thought the move was “extremely effective against the cartels and completely legal.”

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“He’s created No Trespassing zones on the border, and by taking federal land and declaring a national emergency and transferring it to the military, and then also using the military as an exception to the Posse Comitatus Act where he says, ‘This is a military purpose to deal with the emergency on the border.’”

“The idea that the President United States can use a military presence to defend an American border, I think that’s going to be tough to challenge.”

Border militarization accelerates under Trump

Since President Donald Trump took office, the number of active-duty troops at the southern border has surged from under 2,000 to more than 8,000, with Hegseth authorizing up to 10,000 earlier this year.

This militarized approach has also prompted drug traffickers to shift tactics, turning to maritime smuggling routes in response to intensified land enforcement. The Pentagon has responded by deploying naval vessels with Coast Guard teams to interdict sea-based drug operations.

“We know terrorists are trying to get in through our border,” said Brig Barker, former FBI advisor to U.S. Special Operations Command and counterterrorism expert. “Swarming this with different inter-agencies is a good thing. … The military has a lot of refined skills and capabilities that civilian law enforcement doesn’t have. 

He predicted that military counternarcotics missions would push further into Latin America, “bringing that out to that fight farther out from our border, really kind of preempt before they can get closer to our border.”