A penal colony, prison colony, or rehab colony, were remote prison facilities with characteristics that varied in accordance with the needs and philosophies of their governing cultures. Typically, a sentence to a penal colony differed from normal incarceration by charging the inmate to perform a service or labor, or to help facilitate their own rehabilitation.
Federation penal colonies
In the mid-23rd century, the penal systems of the United Federation of Planets shifted focus from incarceration and punishment to humane rehabilitation, made possible by new technologies and drug therapies. A key figure of this transition was Doctor Tristan Adams. From the late 2240s and into the 2260s, his practices were replicated in many Federation penal colonies, turning what were essentially cages into effective hospitals. Until promising therapies were developed, those few criminally-insane beings deemed incurable and incorrigible were kept in the secure isolation of Asylum facilities. (TOS: "Dagger of the Mind", "Whom Gods Destroy")
Ambassador Robert Fox threatened to have Montgomery Scott sent to a penal colony for disobeying his direct orders while Captain James T. Kirk was held captive on Eminiar VII. (TOS: "A Taste of Armageddon")
- Central Bureau of Penology
Enolian penal colonies
Other penal colonies
During the mid-19th century, a penal colony was established on the moon orbiting Mab-Bu VI that included hundreds of prisoners from the Ux-Mal system. As punishment, the prisoners were separated from their bodies and left to drift in the moon's electromagnetic storms. (TNG: "Power Play")
Established sometime prior to the mid-22nd century, the Klingon gulag of Rura Penthe was a prison with no stockade, guard tower, or electrified frontier. Its only form of protection was a magnetic shield surrounding the inhabited dilithium mines to prevent unauthorized beamouts.
The stipulations for the inmates of the prison included the simple fact that no one could escape from below. If prisoners worked well, they would be treated well; if they worked badly, they would be exiled to the asteroid's frozen surface, where nothing could survive for very long.
In late 2152, Jonathan Archer was captured by the Klingons after assisting Arin'Sen rebels. Put on trial on Narendra III, he was sentenced to labor on Rura Penthe, but managed to escape. (ENT: "Judgment")
The Angosian Lunar V colony was created for its genetically-enhanced soldiers who previously participated in the Tarsian War. According to the Angosian government, the soldiers were placed there "for their own protection as well as that of others." Despite the fact that they made every effort to make the colony as amiable for its "colonists" as possible, the fact remained that it was still a prison. (TNG: "The Hunted")
Ennis/Nol-Ennis penal moon
Located in the Gamma Quadrant, this moon served as a place of banishment for the Ennis and Nol-Ennis factions after mediators on their shared homeworld were unable to resolve their conflict. The moon had an automated orbital defense system and its atmosphere contained artificial microbes which would regenerate the dead. Because permanent death was impossible, the Ennis and Nol-Ennis were condemned to fight each other for eternity. In 2369, the Starfleet runabout USS Yangtzee Kiang crash landed on the moon, killing one of the passengers, Bajoran Kai Opaka. As she, too, was regenerated, Kai Opaka decided to remain on the moon to attempt to mediate between the Ennis and Nol-Ennis. (DS9: "Battle Lines")