Star Trek: 10 Things You Didn't Know About The Bell Riots
5. No Criminals Allowed In Our Havens
Star Trek's Sanctuary Districts were designed as 'havens' for homeless people, or financially destitute people, to find shelter, a place to stay, or food. They were also specifically designed not to allow entry to anyone with a criminal record, attempting to shift the perception that they were designed as prisons.
In reality, residents were given very little choice as to their lot in life. Bashir bemoans the lack of medical care afforded to the people he sees in the processing centre, while Sisko describes the Districts as a 'bad mistake' in Earth's history. As he later explains to Bashir, the Districts are a symptom of the overwhelming issues faced by contemporary people. They had given up by this point in history, leading to so many who needed help being deposited inside.
Once inside, there was little chance to leave, as the inmates' stories were never shared with the outside world.