Dude, YOU pay his salary, YOU are his boss. Basically, you're paying him to drive on your grass. I'd start by making it a point to be HOME the next time he comes over. Introduce yourself again, and politely tell him you'd appreciate it if he parked in the driveway and used the doorbell like any other citizen.

Failing that, I'd go straight to his Captain and let him know as a concerned citizen that one of his homeys is using the public dime to land a piece of the poon.