"In both Christain and Jewish theology, God is supposed to be omnipotent. Now, when He made humans, He either did or did not give them free will. If He did, then it follows that He cannot control the acts of humans, which mens He's not omnipotent. And if He did not give humans free will, then the only way God can escape being responsible for the evil humans do is to suppose the He didn't create humans with free will because He coudn't. Again, then, God ends up being denied omnipotense. Thus we have the so-called Paradox of Omnipotence. No matter what God did concerning free will, He cannot be omnipotent, but that is in conflict with an all-powerful God."
Excerted from Time Travel Paradoxes