No, there's no reason to restrict those classes even more. So long as the paladin acts sufficiently like a paladin, he keeps his powers. If he commits evil acts in the name of good--so long as he can rationalize them--he takes no penalty.

Now, if the player gets really out of line, the gods will intervene. Willingly slaughtering an entire village while proclaiming yourself to be lawful good...well, that tends to aggravate the deities who actually are lawful good.