No matter which Green Lantern finds themselves a member of the Justice League, their loyalties may lie elsewhere. One time-honored tradition for the officers of the Green Lantern Corps proves that the interstellar heroes have ultimately given themselves to another cause.
Since DC's premier team of superheroes teamed up to defeat Starro the Conquerer in the pages of The Brave and the Bold #28, there's almost always been a Green Lantern on the Justice League. Though the team has a number of powerful individuals to fight the DCU's many threats, few heroes are as useful as a member of the Green Lantern Corps. With the abilities granted from a Power Ring, Lanterns aid the team by being able to conjure up any weapon or tool needed to overcome any obstacle the team faces. While some officers have had their issues with the structure of the Justice League, Green Lanterns are generally trustworthy members of the team.
However, their infamous credo may have been hinting that the Lanterns aren't as reliable as previously thought. In Green Lantern Corps: Recharge #1 by Geoff Johns and Patrick Gleason the titular organization is rebuilding itself after a long absence. To help it’s many new recruits, the Guardians of the Universe are recalling two of the Corps' most venerated members, Guy Gardner and Kyle Rayner, to active duty on Oa. Before heading out, Guy and Kyle swing by the Justice League and inform the team that they are leaving Earth for the foreseeable future. While Guy treats the moment as an opportunity to take a potshot at Batman, Kyle earnestly discusses the issue with his teammates and lets them know why he has to temporarily leave.
It shouldn’t come as a surprise that Kyle and Guy ultimately have to choose the Corps over the Justice League. After all, the Green Lantern oaths they speak every time they charge their rings aren’t just for show. The oath is an affirmation that Kyle, Guy and any other Power Ring-wielding hero is first and foremost a Green Lantern. So, no matter how consistent their presence has been on the League, any Green Lantern's position on the team is ultimately an ephemeral one.
Unlike heroes like Flash or Superman, the Green Lanterns’ powers aren’t innate to them. People like Guy and Kyle are chosen for their willpower, but their abilities are conditional upon them being on active duty. If they want to remain Green Lantern Corps members, they must abide by the rules and regulations of the Guardians. That means whenever Lanterns are called away to handle business in space, they have no choice but to comply. As independent agents, the other members of the League have freedom that the Lanterns just don't. Even if they'd like to be committed members of the Justice League, the infamous oath is a reminder of whom the Green Lanterns truly serve.