Ever wanted to read someone the Riot Act? Apparently all you need to do is find a group of 12 or more people "tumultuously assembled" and declare the following (preferably with a British accent, of course):
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 tumultuous and riotous assemblies. God save the King.
More information here and here. Thanks to Ken Lammers for the original link. (A bit of Westlaw research suggests that this isn't the entire act as passed in 1715, but it's the part that had to be read to disperse the crowd; anyone who hadn't dispersed in one hour after this was read was guilty of "felony riot." Oh, and no relation to Quiet Riot, at least as far as I can tell.)