why can't bad Locke kill Sawyer according to 'kid Jacob'? only cuz he's a candidate?
the black/white stone def symbolic of good/evil. bad Locke definitely on the evil side
I would guess that's it. There has been refernece to "rules" many times throughout the show (ben when he saw his daughter die, ben when talking to widmore, child jacob to badlocke) not sure if they are the same ones though. My guess is that it's a "free will" type thing so the rules are that you have to let the canidate decide.
I wonder if jacob and the man in black were canidates at one point in their "lives" as well. And they are both looking for canidates to replace them or something. BadLocke made refernces to being a human and then being betrayed. But he could just be spouting off a bunch of crap to get his way. That seems to be the M.O. of everyone on the island…the losties, the others, jacob, badlocke, etc.