A "kangaroo court" means that there has been a fast and unfair legal procedure. It likely comes from during the Gold Rush when American courts would skip procedures for quick sentencing.
“袋鼠法庭”（kangaroo court）指的是美國潦草而不公正的審判程序。這句話有可能來源于淘金熱時期，因為那個時期的法庭為了快速判決會省略掉一些程序。

Even though Kangaroos are native to Australia, this phrase dates back to the 19th century Gold Rush in America.
盡管袋鼠是澳大利亞獨有的動物，但這句話始見于19世紀美國淘金熱時期。

The most likely origin of the phrase, according to researchers, is that people who saw the quick sentencing in American courts during this time likened it to kangaroos hopping or skipping.
研究者稱，在淘金熱時期，人們在法庭上會經常見到快速潦草的審判，而袋鼠是蹦跳著走路的，因此人們把袋鼠的蹦跳比作法庭省略程序的做法。