an Act passed by the British government in 1715 and repealed in 1967, designed to prevent civil disorder. The Act made it a felony for an assembly of more than twelve people to refuse to disperse after being ordered to do so and having been read a specified section of the Act by lawful authority.
read someone the Riot Act
British give someone a severe warning or reprimand:he read the riot act to his players after hauling them in for extra training
Riot Act in other Oxford dictionaries
Definition of Riot Act in the US English dictionary