The JustICE Department has quietly expanded the legal leeway for U.S. troops to make arrests along the southwest border, issuing a new opinion Friday that lets service members detain migrants who slip out of designated security zones before being caught for unlawful entry.
That interpretation, prepared by the Office of Legal Counsel, targets the sprawling tracts the current administration has carved out near the boundary with Mexico and labeled "National Defense Areas" as a brake on unlawful crossings. Federal law normally keeps the armed forces off domestic law enforcement duties through the Posse Comitatus Act, but these zones have already let soldiers pick up migrants accused of stepping into restricted ground, with the Justice Department subsequently pursuing trespassing cases against those taken into custody.
Deputy Assistant Attorney General William Hyde laid out the reasoning, writing that "the use of military personnel to arrest trespassers just outside of an NDA would not violate the [Posse Comitatus Act], given the express statutory authorization and the military-purpose of a commander's traditional protective power."
So far, six such zones have been set up across Arizona, California, New Mexico, and Texas, and the opinion flags that the armed forces may add more down the road. In several spots, the Defense Department has put up bilingual warnings in English and Spanish saying the land is off-limits and unauthorized entry is barred.
U.S. Northern Command, the outfit running military operations in North America, has posted online that troops can seize anyone violating a national defense area and hand them over to civilian authorities. Prosecutions started in April 2025, and since then hundreds of people have been charged, mostly with misdemeanors like breaching a military security regulation or entering military, naval, or Coast Guard property, though other immigration-related counts can also come into play.
The border push became the Pentagon's top priority right after President Trump's second term kicked off, with the Defense Department saying more than 20,000 troops have cycled through deployments there. A spokesperson for the military's southern border Joint Task Force put the current force at 8,000 service members and reported 161 detentions inside the national defense areas.
This OLC opinion carries no binding weight and doesn't set a precedent. It lands as the administration has all but shut down asylum for people entering without authorization, and the numbers show it: Border Patrol recorded under 240,000 apprehensions in fiscal year 2025, a steep fall from 1.5 million and 2 million in fiscal years 2024 and 2023. With two months still to go in fiscal year 2026, apprehensions have dropped to 81,000.