The other answers are all good, but if you are asking how to do it legally, you need to check your state's laws and cases, and if you can't, you really need to check with a lawyer who does evictions.. . Another way is to change the locks when they are out.. . Not all state allow self-help evictions, so if the in-laws are likely to go to a lawyer if you try to throw them out, you really do need to chack with a lawyer in your area.