I have heard exorcists on youtube say that for a demon to possess a person, it needs permission to have the legal right. That could be in a ritual or seance or even something as innocent seeming as a ouiji board session. Anything that is an invitation.

Perhaps notifying the public by running things in their faces with movies, books, and music - even satanic half time shows at the Super Bowl would be considered notification. If the public doesn't stand up and reject it en masse, may be tacit consent. I think that is basically the legal theory on how we lost our sovereign citizen status many years ago to the United States Corporation.