I am approaching three years of hosting and the one situation I have never faced is having to call the police on a guest, be it for criminal behavior or to have them removed from the home. In around 185 formal bookings, only *one* ever even approached calling the police. It was very early in my hosting career, and a family of three were dropping hints that they wouldn't leave and planned to just shack up in the house after their reservation ended. I informed them the door code would be changed, the wifi disconnected and their room stripped for cleaning. They then said they would barricade themselves in the room, and then sarcastically asked what did I think I could do about it with three of them and one of me. I stated I would call the police and report them as trespassers. That did the trick, since they were from West Africa and had said earlier in the stay there were some problems with their immigration status and I doubt they wanted to get involved with the police.
That is my sole experience, and I never got as far as actually calling the police. Has anyone else actually crossed that line and called the police on a guest?