There aren’t many circuit court decisions on violations of the Posse Comitatus Act, so the 9th Circuit’s opinion in United States v. Dreyer was bound to catch someone’s attention. Steve Vladick at Just Security explains the PCA:
[A]n 1878 statute that subjects to criminal punishment anyone who, “except in cases and under circumstances expressly authorized by the Constitution or Act of Congress, willfully uses any part of the Army or the Air Force as a posse comitatus or otherwise to execute the laws.”
In Dreyer, that’s what happened:
At issue in Dreyer are the actions of a civilian agent of the Naval Criminal Investigative Service (NCIS), who, without any specific military trigger or target, began an investigation into online criminal activity by anyone in the state of Washington. (Although the PCA’s plain terms apply only to the Army and Air Force, Department of Defense regulations have long provided that the PCA “is applicable to the Department of the Navy and the Marine Corps as a matter of DoD policy.” And although the government argued in Dreyer that civilian agents of the NCIS aren’t covered by those regulations, the Court of Appeals unanimously disagreed.)
