When you read someone the riot act, what you are doing is giving him a severe scolding. You are angrily telling the individual that if the same thing happens again, he will get into serious trouble.
*Listen, you guys! If you don’t clean this mess up, the coach will read you the riot act.
The Riot Act was a law that came into effect in Britain in 1715. This law had to be passed because of the unstable political situation in the country. The Riot Act made it illegal for 12 or more people to assemble in
public places. Whenever a group gathered, it was the job of the Magistrate or the policeman to stand in front of the crowd and read aloud the Act. If the people did not disperse after hearing the proclamation, they were arrested and put in prison, sometimes for several years!