Originally Posted by The Joker
It's simple. The only pieces of info that the movie gives about how the Dent Act works is that it denies convicted criminals parole, and it lets women be put in the male wings of a prison.
So some are wondering how did an Act that only affects people already in prison clean up a city as dirty as Gotham? The truth is the movie doesn't give any insight as to how it does that. That's where the waves of conjecture come in.
Although with Gotham City being clean of organized crime, you have to suspect that the Dent Act calls for much more even if not mentioned during the film.