Kangaroo Courts are not all that negative, however. They can be used as a means of diversion
A long time ago in a since-lost copy of InQuest magazine, I stumbled across a rules variant for Magic: The Gathering, named Kangaroo Court Rules. In this game, there are the normal two players, but there is also a judge. The judge's responsibility is to rule on arguments by the players as to the validity of certain moves. For example, say Player 1 has a Blood Moon, and Player 2 puts a Bad Moon into play. Player 2 could propose that since there can't be two moons, Player 1's Blood Moon should be removed from the game. At this point, the judge considers it and renders a verdict. Smart judges will record their decisions, as over time precidents can change the face of such games.
Also, some professional sports teams (notably the Denver Broncos, who run a kangaroo court so popular that SportsCenter did a report on it) run kangaroo courts. These consist of "fines" for such things as scoring a touchdown, partaking in a bad victory dance, or appearing on television or being quoted on the news. At the end of the year, the money collected from these fines goes towards the year-end team party.