Use and Enforcement: Easements

My question involves an easement in the state of: I purchased my land (20 acres) in MT. I now have a neighbor who just constructed a building, maybe a home, just off the roadway, which all have the right to use. This neighbor now is taking it upon himself to fix the roadway, which is fine, but he is grading onto my property. I called the Yellowstone County Sheriff to get a stop and desist order since this is taking away from my property. The deputy called me back stating that he was informed by this neighbor that there was a forty foot easement, but there was no documentation to show that. The deputy then stated that this neighbor was helping improve the road and was doing nothing to stop it. This is telling me that the law enforcement is allowing this neighbor to continue trespassing onto my property and extending the width of the road onto my property without even digging onto his own property. What can I do to stop this from happening? I marked off, with paint on my property where the edge met the road and it is now gone. The distance from the edge of the road to the posts I put in is getting narrower. What can I do? I've had problems with these people since day one they came in to build.

Use and Enforcement: Easements