So then what's going on with Justice League? Our best guess is that either before the movie or early into the story, the Green Lantern of Sector 2814 has either been "dealt with" or is "occupied elsewhere," to use as loose of terms as possible. If the Green Lantern who is supposed to look after that sector is an alien, then they're most likely dead, as DC wouldn't risk killing off one of the human Green Lanterns so soon. If the Green Lantern is Abin Sur, then his demise could potentially serve as an adaptation of Hal Jordan's origin. Abin Sur tries to stop Steppenwolf from reaching Earth, and is fatally injured in the process. From there, the ring selects its new wielder within that sector, and whether Hal gets to meet Abin Sur like he did in the comics and the 2011 Green Lantern movie or doesn't come face to face his predecessor, he would be transported to Oa for training, hence why a Green Lantern isn't aiding Batman, Wonder Woman, Aquaman, Flash and Cyborg in battling Steppenwolf and the Parademons.