Mega City One has been through an awful lot over the past few years. Not only is there the usual crime that comes with being a fascist future state, but the city's also had to deal with stuff like the Chaos Plague, space lasers, all sorts of other problems. It's got so bad, in fact, that the city's 40,000 wealthiest citizens have got together to buy a spaceship and just get the heck out of Earth before something else happens.
That's where John Wagner and Greg Staples' Judge Dredd: Dark Justice picks up, with the launch of the Mayflower into deep space. Oh, and also the Dark Judges, the genocidal, immortal, inter-dimensional entities who see life itself as a crime, and punish it with mass murder are also coming back. So, you know, I'll let you guess how well that's gonna work out for 'em.