Posse Comitatus

Posse Comitatus ('the posse of the county')—the infinitive 'to be able' being used in late Latin as a noun, and meaning power or force), the whole force of the county, consisting of knights and men above the age of fifteen, with constables, who attend the orders of the sheriff to assist in enforcing process or quelling riots. Justices of the peace can also, if apprehensive of an organised resistance, command the services of the posse comitatus, and it is the sheriff's duty to raise the necessary number of men. But practically, in modern times, constables and special constables are all the assistance given or required. See SHERIFF.