The film takes place in 2080 and depicts a dystopian world and the crime- ridden metropolis Mega-City One. Following an unspecified disaster that turned Earth into a "cursed" wasteland, the survivors established a corps of Judges whose role combines that of police, judge, jury and executioner. The film follows Judge Joseph Dredd, one of the most dedicated Street Judges who had been framed for murder by his own half-brother, the hardened criminal Rico.

References:
https://en.wikipedia.org/wiki/Judge_Dredd_(film)