(covers information from several alternate timelines)
Starfleet Rehab was the branch of Starfleet responsible for the rehabilitation of former Starfleet officers and enlisted personnel. Prisoners were treated at settlements administered by this branch. One of these settlements was the New Zealand Penal Settlement.
In an alternate 2372, Tom Paris related to Harry Kim that the reason he had taken Kathryn Janeway up on her offer to serve on USS Voyager in 2371 was because it sounded better than Starfleet Rehab. (VOY: "Non Sequitur")