Star Trek: Voyager
Episode: VOY 147 - Chute, The

Advanced humanoid Delta Quadrant race with basic interstellar spaceflight, perhaps warp-capable. A dictatorship controls the planet, now dealing with an Open Sky group fighting to overthrow it.

Felons are kept in an isolated spacegoing station — as the U.S.S. Voyager's Paris and Kim discovers when wrongly sent there.  Pardons or rehearings in convictions and sentencing are never heard.