-You can not stop them to enter U.S. because they have a valid visa.
不知美國的限製令(restrain order, based on mental abuse)可否通用於未入境的人士?
-No such a law in your parents'case. But you can ban them to enter your house from the law point of view, but I do not think you will do that.
家門不幸,多謝大家的體諒!