Kangaroo court

Kangaroo court, unofficial and illegal gathering of unauthorized persons for the purpose of passing sentence upon a wrongdoer. Such sentences have been imposed in many countries by citizens' groups, such as vigilante societies in the United States and the illegal Irish Republican Army. The name was first used c.1853 to refer to the “instant justice” meted out by frontier judges in the United States who “hopped” like kangaroos from place to place on their legal circuits.