Dent Act

Dent Act was a law that was passed after the death of Harvey Dent. It was a law that was so effective that it virtually wiped out all of crime in Gotham City for eight years after the Joker's reign of terror upon Gotham City as well as the death of Dent himself.

The Dark Knight Rises
"This man has been given to you as the shining example of justice! You have been supplied with a false idol, to stop you from tearing down this corrupt city! Let me tell you the truth about Harvey Dent from the words of Gotham’s police commissioner, James Gordon. "The Batman didn’t murder Harvey Dent, he saved my boy, then took the blame for Harvey’s appalling crimes so I could, to my shame, build a lie around this fallen idol. I praised the madman who tried to murder my own child, but I can no longer with my lie. It is time to trust the people of Gotham with the truth, and it is time for me to resign.""

- Bane

The Dent Act was presumably eliminated after Bane with the speech he stole from James Gordon, which he read outside of Blackgate Prison, which was a revelation of what Harvey Dent did after he lost Rachel Dawes at the hands of Joker's thugs. This definitely prompted the inmates of Blackgate to riot before they were "liberated" by Bane's men.