Warning: Spoilers for DCeased: War of the Undead Gods #5 ahead!DC's intergalactic peacekeeping force, the Green Lantern Corps, has a problem with authority that fundamentally breaks the Corps as an organization. Although the Corps is dedicated to their job and to each other, the fact that they are constantly at odds with their leadership (usually the Guardians of the Universe, but not always) means that they can never be trusted to follow the rules and protocols set in place to keep their incredible powers in check. In essence, this turns the Corps into a paramilitary group that is functionally answerable to no one - the exact kind of threat that the Guardians sought to prevent.
The Corps and the Guardians are almost always portrayed as being at odds with each other, especially when seen through the lens of its human members such as loose-cannon Hal Jordan and least popular Lantern Guy Gardner. To them, the Guardians hide behind rules and red tape, preventing the Corps from taking action and fixing issues. Although they have been reprimanded by the Guardians time and time again, repercussions for their insubordination rarely seem to bench them for long: a side effect of filling the Corps with the most stubborn and willful beings in the universe.
The relationship between the Corps and the Guardians is summed up handily in Tom Taylor, Trevor Hairsine, Neil Edwards, Andy Lanning, and Rain Beredo's DCeased: War of the Undead Gods #5. When Corps member Kilowog learns that his home of Bolovax Vik is under attack by Darkseid and his undead, he departs for the planet despite the Guardians expressly forbidding it, fearing the thinning of their forces. He's promptly joined by a sizable retinue of Corps members including Guy Gardner and John Stewart, who scoff at the Guardian's orders: "Lotta rules. Not a lot of loyalty."
The Fundamental Flaw of the Green Lantern Corps in One Sentence.
Although this moment is meant to be a heartwarming show of support for Kilowog, it turns into a bloodbath when the Corps is slaughtered by an undead Mr. Mxyzptlk - the kind of atrocity that the Guardians specifically sought to avoid. If the Green Lantern Corps freely ignores the protocols and rules that the Guardians need them to abide by, then they're scarcely better than the Manhunters (the rampaging machines that the Corps eventually replaced). It's a small wonder that the Guardians have sought to restrict the Corps' power time and time again.
This is not to say that the Guardians have not committed crimes themselves; their pursuit of emotionless logic, they have committed blunder after blunder (such as when they tried to replace the Corps with the disastrous Third Army). Nonetheless, the Green Lanterns serve essentially as the police force of the DC Universe, and such an agency needs to be transparent and accountable in its actions for its authority to have any weight. "Lotta rules. Not a lot of loyalty" perfectly encapsulates why the Green Lantern Corps is fundamentally broken as an organization.
DCeased: War of the Undead Gods #5 is now available from DC Comics.