read the riot act

read (someone) the riot act

to speak angrily to someone about something they have done and warn them that they will be punished if they do it again. He'd put up with a lot of bad behaviour from his son and thought it was time to read him the riot act.

See also: act, read, riot

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read someone the riot act

to strongly warn someone to stop behaving badly. Alice read Randi the riot act, telling her, “If you don't like it here, you can just go back where you came from.” The secretary of state said she plans to read the riot act to the country's leaders during meetings next week.

lay down the law

Etymology: based on the Riot Act (= an English law of 1715 that provided a way to deal with a crowd of people who were causing trouble)

See also: act, read, riot