According to Wikipedia, there is some debate over the origin of the term “kangaroo court”, but some sources suggest that it may have been popularized during the California Gold Rush of 1849.
It also indicates that many Major League Baseball teams have a kangaroo court to punish players for errors and other mistakes on the field, as well as for being late for a game or practice, not wearing proper attire to road games, or having a messy locker in the clubhouse. Fines are allotted, and at the end of the year, the money collected is given to charity. The organization may also use the money for a team party at the end of the season.
The Herts Falcons Kangaroo Court is a little different, as this video from the latest court session would suggest.