How do you get rid of a roommate not listed on the lease?

If you have a valid reason for wanting this person out, you have to give a week's notice, if this person pays by the month, a month's notice, or if seriously behind in paying rent 24 hours! As long as they are not on the lease they do not have recourse, a good idea is though whomever is on the lease will tell the person their tenancy has stopped.