Read the riot act
Reprimand rowdy characters and warn them to stop behaving badly.
Since the early 19th century we have used 'read the riot act' as a figurative phrase to describe attempts to calm groups of rowdies - along the same lines as 'you noisy louts, don't you know there are people here trying to sleep?'. It wasn't always so. Had we been 'reading the riot act' in 1715 we would have noticed capital letters. At that date there was a real Riot Act and it used to be read in public.
In English law the control of unruly citizens has usually been the responsibility of local magistrates. Any group of twelve or more that the authorities didn't like the look of could be deemed a 'riotous and tumultuous assembly' and arrested if they didn't disperse within an hour of the Riot Act being read to them by a magistrate. This seems a little harsh, but in 18th century England the government was fearful of Jacobite mobs who threatened to rise up and overthrow the Hanoverian George I. The fear was well-founded, as supporters of the deposed Stuarts did actually invade in 1715 and again in 1745. The 'Riot Act' was passed by the British government in 1714 and came into force in 1715. The Riot Act, which was more formally called 'An act for preventing tumults and riotous assemblies, and for the more speedy and effectual punishing the rioters' actually contained this warning:
"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, for preventing tumults and riotous assemblies. God save the King."
The punishments for ignoring the Act were severe - penal servitude for not less than three years, or imprisonment with hard labour for up to two years.
After the Hanoverians were established in power the Riot Act began to fade into disuse. It was read to a group of demonstrating mill workers at Manchester Town Hall in 1842, but was used with decreasing frequency and had become a rarity by the 20th century. Surprisingly, the Act remained on the UK statute books into modern times and wasn't formally repealed until 1973. It was eventually superseded by the 1986 Public Order Act.
The first record of the figurative use of the phrase is in William Bradford's Letters, December 1819:
"She has just run out to read the riot act in the Nursery."