Posse Comitatus Definition: The emergency roundup of a group of civilians or soldiers to address a significant civil law enforcement crisis. In United States v Garcia, Justice Kravitch of the United States Court of Appeals adopted this definition of posse comitatus:"The power or force of the county. The entire population of a county above the age of fifteen, which a sheriff may summon to his assistance in certain cases, as to aid him in keeping the peace, in pursuing and arresting felons, etc." In the United States, it is now illegal to convene a posse comitatus comprised of members of the armed forces (18 U.S.C. ยง1385).REFERENCES:Meeks, Clarence, Illegal Law Enforcement: Aiding Civil Authorities in Violation of the Posse Comitatus Act, 70 Mil.L.Rev. 83 (1975)United States v. Garcia, 672 F. 2d 1349 (1982) Categories & Topics: Criminal Law Dictionary Military Law Dictionary Find you are constantly looking up definitions? Try our search provider (works in most modern browsers) If you find an error or omission in Duhaime's Legal Dictionary, or if you have legal term suggestion, we'd love to hear from you!