Is it permissible to prevent a smoking visitor from entering one's apartment, and what should one do with a guest who wishes to smoke in one's home?

You do not have the right to prevent your wife's father, who smokes, from visiting his daughter merely because he is a smoker. However, you can order him or your wife to advise him to stop smoking inside the house. If he insists on smoking inside your home, then you have the right to prevent him from entering, due to the harm that would result to the household members, as the Prophet (peace be upon him) said: "There should be neither harming nor reciprocating harm," and according to the principle: "Harm must be removed."