I guess one of the two. State nicely at the beginning that things have to be in a certain way and they have to strictly adhere to the rules. Or else, don't say anything and endure the discomfort until they are finally gone.
I once was asked by a "friend" if I would be too uncomfortable if she stayed at my place because she was being kicked out of her rented place. I honestly told her she could stay till she found a new place, but it would be very uncomfortable for me to have someone else at my place. She decided not to stay at my place for whatever reason. I felt bad, but I just wanted to be honest.