In 1714, British Parliament passed the Riot Act, a law that discouraged unruly mobs from public protest. What was rendering mobs unruly in those days was general dissatisfaction with the newly-crowned King George 1, who was not a fellow Briton, but a blunt and domineering German who could not even be bothered to learn the English language.
The Riot Act was designed to make felons of those who would publicly threaten the monarchy. Under the Act, a magistrate or sheriff could order the dispersal of a dozen or more protesters by reciting the Law, which read:
Our sovereign Lord the King…commandeth all persons, being assembled, immediately to disperse themselves, and peaceably to depart to their habitations, or to their lawful business, upon the pains contained in the act made in the first year of King George, for preventing tumults and riotous assemblies. God save the King.
Then, if the protestors did not disperse within one hour of the proclamation of the Riot Act, they were sentenced to imprisonment or hard labor. For many decades after the days of King George, the Act was invoked to extinguish any public misbehavior.
Though the Riot Act was repealed in Britan in 1973, the expression to read the riot actbecame verbal shorthand for the notion of delivering someone a warning or a severe reprimand.