One tragic event forever changed the course of history on Earth-50: President Lex Luthor publicly, and personally, executed the Flash. Superman, tormented by what Luthor had done, took violent retribution, using his heat vision to murder his long-time nemesis.
This incident drove the angry and grieving Man of Steel to conclude that the only way to protect the world from super-villains like Luthor is by eliminating them, using violent means if necessary. He reformed the Justice League as the Justice Lords, determined to preserve peace on Earth by instituting permanent martial law, justifying their brutal actions as a temporary necessity to save the planet.
Over time, Earth-50 descended into a fascist police state, ruled over by the tyrannical, super-powered and self-serving Lords. The Watchtower became a headquarters for worldwide surveillance, aiding the Lords in suppressing free speech and democratic elections.
Only one Justice League member does not agree with the Lords’ schemes—Batman. Operating in secrecy from his cave, the Dark Knight follows his own personal code, forming the heart of the only significant opposition to Superman’s totalitarian plans for worldwide domination.
BATMAN BEYOND UNIVERSE #9 (2014)