On August 14, 2026, the U.S. Justice Department issued a legal opinion that expands the military's authority to detain migrants accused of trespassing in areas controlled by the Department of Defense. This decision is part of the Trump administration's efforts to enforce immigration laws at the southern border. The opinion specifically addresses areas designated as "National Defense Areas" (NDAs) near the U.S.-Mexico border, where military personnel can detain individuals for trespassing.
The Posse Comitatus Act generally prohibits the military from enforcing laws domestically; however, the establishment of NDAs allows for military involvement in apprehending individuals who enter these restricted zones. Deputy Assistant Attorney General William Hyde stated that military personnel can arrest individuals who leave these areas before they can be apprehended for trespassing.
Currently, six NDAs have been established along the southern border in Arizona, California, New Mexico, and Texas, with the potential for more to be designated in the future. The military has placed signs in both English and Spanish in these areas to inform the public of the restrictions.
U.S. Northern Command has indicated that military personnel can apprehend trespassers and transfer them to law enforcement. Since the implementation of this policy, the Justice Department has charged hundreds of individuals for trespassing in these areas. In fiscal year 2025, Border Patrol reported a significant decrease in migrant apprehensions, with fewer than 240,000 reported, down from 1.5 million in fiscal year 2024.