I believe that the laws of God apply to Satan just as much as they do to man. The only way he can steal souls is if people sign the contract legally. There are laws about disclosure and so Satan does disclose what he is doing, but he does it with people that everyone dismisses. He may use the Simpsons, or some cheesy movie, or some guy who has dementia or a vice president who comes across as the biggest idiot in the world.