When I was reading it as a lad I always thought it was a parody of American culture, policy and law enforcement. A true sci-fi western. Substitute Judge for Marshall, guns with the right bullets solve everything and really long sentences or death fix all the problems of the society.

The joke being that Dredd never ever has any real impact on the society.

Oh and Tharg's Future Shocks did it way before and better than Black Mirror!