Reading the Riot Act

The Riot Act of 1714 provided that if English authorities encountered any group of more than 12 persons they thought looked like a riot they could order those people to disperse, and anyone who did not could be charged with a felony.

The actual proclamation they read out went like this:

Our Sovereign Lord the King chargeth and 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 the First for preventing tumults and riotous assemblies.

GOD SAVE THE KING.

That was called "reading the riot act."