Posse comitatus

An American posse in 1922, which captured the outlaws Manuel Martinez and Placidio Silvas, who are in the center of the back row. Martinez and Silvas were arrested for the Ruby Murders after the largest manhunt in the history of the Southwest.^[1]

Etymology

Derived from Latin, posse comitātūs ("force of the county/region") is sometimes shortened to simply posse from the mid-17th century onward to describe the force itself more than the legal principle.^[3]

While the original meaning refers to a group of citizens assembled by the authorities to deal with an emergency (such as suppressing a riot or pursuing felons and outlawry), the term is also used for any force or band, especially with hostile intent, often also figuratively or humorously.^[4]

In 19th-century usage, posse comitatus also acquired the generalized or figurative meaning.^[5]

In classical Latin, posse is a contraction of potesse, an irregular Latin verb meaning "to be able".^[6][7][8]

The unusual genitive in "-ūs" is a feature of the fourth declension.

In its earliest days, the posse comitatus was subordinate to the king, country, and local authority.^[9]