You'd have the person arrested for harassment.
In a functioning democracy, it's not the thickness of the doors that prevents them from being kicked in, but the strength of the laws that restrains those who would do the kicking. Likewise, the "reasonable expectation of privacy" is not limited to the narrow range of situations in which violations are physically impossible, but the much broader range of situations in which violations are corrosive enough to be socially and politically unacceptable.