An Idea why John is in Kyle's sector.

[Samurai Rocko]

Heres a thought. How about Kyle Rayner and Superman are battling Dr. Light and are losing badly. Dr. Light knocks Kyle across Metropolis where normal guy John Stewart is. Kyle falls on the ground knocked out and Kyle's ring falls off. John puts on the ring and battles Dr. Light and defeats him. When the guardians of the universe found out what happen they made John the protecter of our sector and reassighned Kyle to a different sector.

[DCU Bat]

I always thought it was because Kyle went away for training and The guardians decide to assign a vetrian GL in his absense (who was currently assigned to a different sector) and who better than John Stewart.

[Ed Liu]

Howdy,

The rings don't work that way. From what I understand, they're reasonably intelligent, and won't work for anybody except their designated bearer. The only way the ring will accept a new owner is if the old one dies or explicitly orders the ring to go to someone new.

-- Ed/Ace

[Jor-El]

Great Book of Oa: Power Rings (http://www.glcorps.org/rings.html)

That is an EXCELLENT study of Power Rings and how they work. I would even call it "scholarly"