Anything other than this would violate the basic but universal "law of free will."
This position is supported by many, many discussions with theologians, priests, and ministers and by writers on the topic of possession and exorcism like Malachi Martin (Hostage to the Devil) and, to a lesser degree, Scott Peck (People of the Lie).
That said, it is possible that something, some exception, has been overlooked.
The only Person with the power to control the fallen angels is Jesus Christ and if a person chooses not to accept Him as Savior, then they are vulnerable to anything happening to them and they have no way to defend themselves and no protection.
I was referring to the entry by demons into a soul that is empty, a place that is not filled with the fire of Jesus Christ, which keeps all demons away.
It's not an easy concept. It's not as easy to understand as a deal made with the Devil. It is biblical, however. And if you think about it makes sense.