The no-killing rule was abolished during the War of Light. Not everyone in the Corps liked that.

The rings don't do things the lanterns will, they create hard light constructs and are powered by willpower.

I could be wrong but I think the no killing rule went back into effect by the end of Hal Jordan and the GLC.

@PoolDeadpool2 No. Green Lanterns can’t “will” anything to happen. That’s not how their powers work.

Don't take the "will" part too literally. The Green Lantern rings draw their power from the user's willpower, yeah, but that "will" is just their ability to overcome fear. The only thing they can "will" the ring to do is to create solid green light constructs from their imagination. And in very rare occasions (I could be wrong tho), the ring is capable of curing or reviving a person, but it requires a massive amount of willpower.

Ok thanks all of you.

@Leto2073 Never been a fan, and wish they didn't overcomplicate him so much. He's a superhero with a magic ring, why do there have to be full corps and all this willpower crap?

I don't know what to say, your understanding of GL is even less than superficial.

Never cared about the character enough to devote my time to understanding everything about him. And I was also half kidding with that statement.

Johns’ Green Lantern Rebirth did not complicate the mythos. He enriched it while making sense of seemingly trivial elements introduced in the SA.

The SA series that ‘conveniently’ treats it as a magic ring raises far more questions of logic. Johns actually simplified the rules. Hal was doing all sorts of ridiculous feats in the SA that literally did will the impossible that had nothing to do with light constructs. It was a mess.