Justice Department authorizes broader military arrests of migrants in border defense zones

On Friday, the Justice Department’s Office of Legal Counsel released a legal opinion that broadens the scope for U.S. service members to apprehend migrants accused of trespassing in National Defense Areas along the southern border. The memo, authored by Deputy Assistant Attorney General William Hyde, contends that arrests made just outside these zones comply with the Posse Comitatus Act due to specific statutory authorization and the traditional protective role of commanders.

Currently, six defense zones have been established across Arizona, California, New Mexico and Texas, and the military may designate additional areas. Signs in English and Spanish warn that entry is prohibited, and U.S. Northern Command confirms that service members can transfer detained individuals to civilian law-enforcement agencies. Since the policy began in April 2025, hundreds have been charged with misdemeanors for violating military security regulations or entering naval or Coast Guard property. The opinion is advisory and does not set precedent, but it supports the administration’s broader crackdown on illegal immigration, which has coincided with a sharp decline in border apprehensions.