Decades after Black Canary (Dinah Lance), Green Arrow (Oliver Queen), and Huntress (Helena Bertinelli) joined the Justice League a mystical being, and associate of Lex Luthor, named Tala revealed to the world that the long conflict between the Justice League and the Legion of Doom was brought about through the design of Jor-El, a Kryptonian. Tala revealed that Jor-El had programmed Lex Luthor and Kal-El (AKA Superman) so that neither one could ever completely destroy the other. Instead a balance was to be maintained, keeping the Earth in an unending war.
This claim by Tala was confirmed by several members of the Justice League who had mystical powers similar to hers.
Many metahumans on both sides of the conflict abandoned their leaders. Within the Justice League Green Arrow was one of the most vocal of the ones to leave. Black Canary was one of the most vocal of those to stay. Oliver tried to convince her to leave.
Oliver: “Come on now, Dinah. It's time to go. Are you going to stay here and serve the Kryptonian?”
Dinah: “Oliver, we took an oath.”
Oliver: “The code. Where has our code led us? Are we slaves to this Jor-El?”
Dinah: “The code contains my ideals. If you reject the code you reject me.”
Oliver: “I won't be a pawn, Dinah. We can destroy the fortress. Reject the lie and join us. It'll be just like before we joined the league, back when we took on the gangs of Metropolis--just you, me and Helena. We ruled the city.”
Dinah: “Those gangs wanted to be gods, Oliver. I don’t want to be a god.”
Oliver: “I just want to make it like it was before the lie! I just want to be free!
Dinah: “Oh, Oliver. I’d like to help you. I’d like to be free, but I can’t. I’m not sure who’s right, and who’s wrong, but it doesn’t matter. I’m Justice League. Sometimes you just have to do what you’re told. That’s who we are.”
Oliver: “Let’s go,
Oliver: “We’ll never be part of their council, Helena.”
Oliver: “Fine. You two have made your choice. I'm gone."
(Photos from left to right: Katheryn Winnick from the movie 'Amusement', Ashley Scott as Helena Kyle from the TV series 'Birds of Prey', Matthew McConaughey from the movie 'Reign of Fire')