Believing that Green Lantern is being tried unfairly in the galactic court, the Leaguers decide to do some digging of their own. The Flash mounts a defense (of sorts), while Hawkgirl tries to motivate John's fellow Green Lanterns in her own unique method (i.e., she slugs them), and Superman and J'onn investigate the scene of the destroyed planet.
As the case moves on, the Guardians of the Universe, the ones who created the Green Lantern Corp, enter as witnesses, but make the mistake of leaving the cradle of the Green Lantern power, Oa, partially unguarded. Superman and J'onn realize that John has been framed: the Manhunters, former android servants of the Guardians, concealed the planet with a cloaking device and plan to destroy the seat of their former masters' power. They framed John Stewart to draw out the Guardians and weaken their defenses, since they themselves power the Central Lantern.
The Manhunter armies launch a mass assault but the Justice League delay them long enough for John to enter the Central Battery and prevent the Lead Manhunter from acquiring all of the Guardians' power. John is cleared of all charges and, relieved, returns to Earth with the League.
Guardians of the Universe
The Guardians are at the heart of the Green Lantern Corp, both literally and figuratively. They first appeared in Green Lantern (vol. 2) #1. A humanoid species evolving on the planet Malthus 10 billion years ago, they super-evolved about 5 billion years later, becoming effectively immortal and able to channel vast energies through their bodies. After a failed effort by one of their number to investigate the beginning of the Universe, they resolved to fight evil and formed android operatives - the Manhunters. They rebelled and became power-hungry and the Guardians stripped them of their power and banished them. The Guardians eventually decided sentient beings would make the best "policemen." They focused their power through a great battery, which would feed green energy to their 3600 "Green Lanterns" who could wield and shape it through sheer willpower.