Star Trek: Enterprise: North Star

Archer, Trip and T'Pol head down to a planet where humans are living in a wild west-like society. Archer learns that aliens named Skagarans brought humans from three hundred years ago there for slave labour, but the humans resisted and turned the tables on them. Now the humans' descendants are in charge and the Skagarans are forced to endure prejudice and unfair laws. The crew have to decide what to do with the humans and the prejudice will lead to a showdown.