A mock court: The toughest prisoner announced that he was president of the Kangaroo Club and would hold court(1853+)
A small-town police court where traffic fines to transients are high and usually divided among the police (1940s+)
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with kangaroo-court
A self-appointed tribunal that violates established legal procedure; also, a dishonest or incompetent court of law. For example, The rebels set up a kangaroo court and condemned the prisoners to summary execution, or That judge runs a kangaroo court—he tells rape victims they should have been more careful. This expression is thought to liken the jumping ability of kangaroos to a court that jumps to conclusions on an invalid basis.