Can a landlord dictate who can and can't visit a home and how long they can stay?

My uncle's landlord told him that my cousin's boyfriend was allowed to visit but that he can't stay the night at my uncles house anymore and that he could visit but he was not allowed to stay all day. The landlord said that his car would be towed if it happened again. He also is making my uncle kick out his son's girlfriend today without any notice at all. He says she has to be gone today or they all have to get out. Can he do this legally?