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DOJ legal opinion expanded military's arrest authority beyond southern border National Defense Areas

On August 14, 2026, the U.S. Department of Justice's Office of Legal Counsel issued a formal opinion concluding that military personnel may arrest migrants for trespassing even after they leave one of the six "National Defense Areas" the Trump administration has designated along the U.S.-Mexico border in Arizona, California, New Mexico, and Texas. Deputy Assistant Attorney General William Hyde wrote that arresting trespassers "just outside of an NDA would not violate the [Posse Comitatus Act]," citing a commander's traditional protective power over military property. The opinion, issued in Washington, D.C., extends military detention authority beyond the National Defense Areas' boundaries for the first time since the zones were created in 2025.

Jurisdiction
Federal
Location
Washington, D.C.

Abuses documented

Actors

On August 14, 2026, the U.S. Department of Justice's Office of Legal Counsel (OLC) issued a formal opinion concluding that military personnel may arrest people who trespass on a "National Defense Area" (NDA) along the U.S.-Mexico border even after they leave the zone, so long as the arrest happens in its "immediate vicinity." Deputy Assistant Attorney General William Hyde, who signed the opinion, wrote 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." The military has established six NDAs since April 2025 -- in Arizona, California, New Mexico, and Texas -- and the opinion noted more zones may be designated in the future.

The Posse Comitatus Act generally bars the armed forces from acting as civilian law enforcement absent express statutory authorization. Military authority to detain trespassers had previously been confined to inside NDA boundaries, where soldiers held people for transfer to civilian law enforcement, which could then charge them with trespassing on military land. Hyde's opinion extends that authority beyond the boundary, reasoning that a commander's statutory duty to protect military property does not stop at the NDA's edge and that no separate "military nexus" is required to justify an arrest just outside it. The opinion itself states it is "advisory only," sets no legal precedent, and does not license the military to enforce civilian law generally.

The Justice Department began prosecuting NDA trespassers in April 2025 and has since charged hundreds of people, mostly with misdemeanor violations of military security regulations. A spokesperson for the military's southern border Joint Task Force -- about 8,000 service members -- told CBS News the task force has made 161 detentions in NDAs to date. As of this writing, no lawsuit has been filed challenging the August 14 opinion, and no named legal expert or civil-liberties organization has publicly responded to it.

Why we recorded this

The Posse Comitatus Act embodies a foundational check on military power: the armed forces do not enforce civilian law inside the United States except where Congress has clearly authorized it. In a formal opinion, the Justice Department's Office of Legal Counsel expanded that exception on its own authority, concluding -- without new legislation or a court ruling -- that military personnel may arrest migrants for trespassing even after they leave the government's designated "National Defense Areas" along the border. An executive-branch legal office unilaterally widening the military's domestic arrest power, based on its own novel theory of a commander's protective authority, is the kind of self-authorized expansion of military policing the Posse Comitatus Act exists to prevent.

Sources

  1. Whether the Posse Comitatus Act Prohibits Military Personnel from Making Arrests Outside, but Within the "Immediate Vicinity" of, a National Defense Area for Crimes Committed Within that National Defense Area — U.S. Department of Justice, Office of Legal Counsel primary accessed August 15, 2026
  2. Justice Department expands military's power to detain migrants accused of trespassing — CBS News investigative accessed August 15, 2026
  3. Justice Department grants military broader authority to detain migrants at border — WTX News secondary accessed August 15, 2026
  4. Justice Dept. says U.S. troops can arrest illegal immigrants beyond military property near border — The Washington Times secondary accessed August 15, 2026

See also