Does he believe you have weed for him? Actually, that'd be rad - if the cops were following this dude, and then are like "Ah, that's the same apartment, six times now."
Dude did some yard work for my parents months ago, now he's coming around all the time and killing my groove.
Sell him some oregano in a baggie, price it up, and make an enemy for life. A stoner-enemy, he will simply just avoid you forever.