It would be better to have him agree to leave with the proper legal papers signed.
p.s. burn everything he wants to eat. ;)
LIsa Y. Forbes (858)459-0581
Michael Spilger (619)232-7761
Most of the answers are correct in that you need to contact an attorney, preferrably Real Estate, that deals with evictions.
HOWEVER!! If it is your house, and he won't leave when you ask him to....you could call the police.
Why would he want to stay where he is not wanted? I know there is a website where you can ask legal questions much like Trulia. I cannot think of the name of it but I used it one time and it was a good experience.