I notice some mistakes in Sinestro's origin

[Fanofthegoblins]

I hear the green lantern ring can not be used by villains. If that's true, then how was Sinestro able to enslave his home planet with the green ring? Also, shouldn't the ring had shut off when he let the Green Lantern, Prohl Gosgotha, die?

[stk]

I hear the green lantern ring can not be used by villains.

1. Where did you hear that?

and

2. Sinestro didn't consider himself a villain.

[Fanofthegoblins]

1. Where did you hear that?

and

2. Sinestro didn't consider himself a villain.

1.) Isn't there a rule somewhere that the ring can not be used by a man commiting bad acts? Don't you have to be worthy?
If bad guys can use it, does that mean The Joker can use it to cause chaos and destruction?

2.) I know, but his actions is evil and immoral. Like Magneto, he doesn't think of himself as a super villain, but he kills people.

[mmehshow]

1.) Isn't there a rule somewhere that the ring can not be used by a man commiting bad acts? Don't you have to be worthy?
If bad guys can use it, does that mean The Joker can use it to cause chaos and destruction?

2.) I know, but his actions is evil and immoral. Like Magneto, he doesn't think of himself as a super villain, but he kills people.

What if it were for the greater good? Just as The Guardians seem to feel? Bad acts and murder are all in the eye of the beholder.

But to try to answer your main question, you must be able to overcome great fear and possess great will to wear a ring. And must be chosen.

So you'll probably never see Joker wearing a GL ring. Mostly because that'd just be retarded.

[Billy Batson]

Why would anyone choose Joker to be a Lantern?

[the4thpip]

Why would anyone choose Joker to be a Lantern?

Because the hair is a great match for the costume?

[fishbonex]

I hear the green lantern ring can not be used by villains. If that's true, then how was Sinestro able to enslave his home planet with the green ring? Also, shouldn't the ring had shut off when he let the Green Lantern, Prohl Gosgotha, die?

I notice some mistakes in OPs thinking of how Green Lanterns work.

[maniacthw]

There is a Sociological concept towards that. You're judging Sinestro by the rules of your culture over the rules of his own culture.

[DrSimonHurt]

The ring only responds to the willpower of the user and is built upon the notion that willpower can only influence righteous actions.

Sinestro was wrong to do what he did to his planet, but he still had will and compassion when doing so. He just made a big mistake.

Plus, they're just space cops. The ring has to trust the choices of the person wearing it. In actuality, infractions against ring-bearers tend to depend on the judgement of the guardians, who aren't known for their compassionate viewpoints.

[dupersuper]

1.) Isn't there a rule somewhere that the ring can not be used by a man commiting bad acts? Don't you have to be worthy?
If bad guys can use it, does that mean The Joker can use it to cause chaos and destruction?

2.) I know, but his actions is evil and immoral. Like Magneto, he doesn't think of himself as a super villain, but he kills people.

The rings are programmed to seek out people who are fearless/can conquer fear and honest...Sinestro is usually that. Any additional judgments are made by the Guardians (and you can see how great their judgment is in the current GL books) and - later - Mogo. Some versions of the ring are only able to be used by the GL unless they say otherwise.

[BraveSirRobin]

Sinestro totally believes he is doing the right thing, despite his obvious mistakes. He is not like the Joker-style "Killing because it's amusing" and by the rules of his own culture, he could even be correct to act the way he does. Quite apart from which, even if he acknowledges he done goofed up, he has conquered the fear that he is going bad, so hey presto! the ring works.

[jackdaw53]

Okay. The OP may have been misinformed in way ring works in DC.

But... jeez... I can see why anybody might believe that any half competent organisation should build some effective safeguards into the "universe's most effective weapon".

I mean looking at past story lines... for example when Hal J took out the entire Corp on his own... it just shows an unbelievable level of incompetence... equivalent to one rogue soldier taking out entire US army on his own. Armies/ police forces don't work like that (I hope!).

[Harbinger of Apocalypse]

Recently, its said that Sinestro knows things about a power ring that no other Lantern knows and this is because the Guardians intentionally like to keep the Lanterns in the dark about the full range of powers available to the rings. Think that was said when Sinestro's run in Green Lantern started and when he changed his costumes colour which was an ability Hal did not know.

[[Trigger]]

Recently, its said that Sinestro knows things about a power ring that no other Lantern knows and this is because the Guardians intentionally like to keep the Lanterns in the dark about the full range of powers available to the rings. Think that was said when Sinestro's run in Green Lantern started and when he changed his costumes colour which was an ability Hal did not know.

This, plus what Maniac said can probably explain it. Good and evil is just what the public of the time believe it to be. Centuries ago people thought it was ok to burn people at the stake and own slaves.