The Justice League assembled in 2012 in response to the Alien Alliance Invasion after the alien invaders had been repelled. Diana Prince, Clark Kent, and Batman were three of the most vocal proponents of the formation of the League. Early members included Barry Allen, Oliver Queen, and Arthur Curry.
The team expanded their roster slowly after the Invasion concluded. Notably they rejected the membership of several side-kicks, including Dick Grayson and Donna Troy for their youth. The League accepted new members over the years on a per-person basis. They were major advocates for the passage of the Alien Resettlement Program and other metahuman legislation.
After the Death of Superman in 2017, the League fragmented over grief and bickering. The charter never wholly dissolved but active membership severely diminished, particularly as Batman returned his focus to Gotham City. They are still an active contingent of superheroes, considered a loose collection of like-minded individual reservists rather than operating as a cohesive team.