Oh look!! I found another thread on ethics, or lack thereof. If you got a bad neighbor stake the ground or use nails, a rifle range with his land and possibly people beyond it, real nice. Do what you can in coordination with your local law enforcementin regards to the trespassing and possible property damage(and I would only do that after talking to the guy, which it sounds like you have done), but if you do anythingother than that you might just start a long term neighbor battle which is always fun .