A long term house guest (typically one that has been in residence a month or more) is considered under the law of most states to be a "licensee". Accordingly, now that permission for them to stay has been revoked, the lawful way to get them removed from the premises is to formally serve them with a notice to leave (it can range from3-30 days, depending on state law). If they fail to leave by the time specified, you will need to file for an "unlawful detainer" (i.e. eviction). If you win in court, then the judge will issue an order for them to vacate. If they still do not move, the sheriff can be called; they will remove the occupant physically if necessary.Note: Until you obtain the court's order, do not take any self help measures such as changing the locks, removing the occupant's belongings, or turning off A/C or utility services to their part of the premises. If you do you could find yourself on the wrong side of a civil suit for wrongful eviction.At this point, you just may want to consult directly with an attorney in your area who specializes in landlord/tenant matters.