It took us a good 5 years of constant vigilance, reporting, and prosecution. Same deal with a bully family that thinks they can do what they want cause it is a birthright. They shot young bucks and hung the circuses on of fences. Our owners live 1 hour to 1 1/2 hours away. The game warden went to have a chat with the patriarch. He was drunk and basically told the game warden he could do what he wanted. The game warden made him a pet project. He followed him around for a season or so checking and citing all his friends for any infraction and suggesting he was not a good friend to have. Other large land owners near us had issues with that family but were scared of repercussions and didn't want the headaches, so they backed off to the bullying. When we stood up and prosecuted, suddenly the other neighbors grew a spine as well.
We did NOT stoop to the tactics of reprisal. That just tells law enforcement it is two bad guys fighting. We simply called law enforcement each and every time we had a trespass and always followed up with prosecution. We use a tool our state has called a Trespass Notice. You fill out a form stating an individual is not permitted on your property. It is served on the individual like a warrant by the local sheriff's office and recorded. Once a trespass notice is in place, judges take it more seriously and the fines go up to the point where jail time can be involved. We used that tool for every trespasser we could identify, including using our wireless camera system. We posted clearly.
No doubt, it is costly and time consuming to deal with court, but if you don't, you send the bullies the message you are a soft target and it never ends. They just get better and hiding it. Eventually the message got out to the community that we were not a soft target. Other neighboring landowners now cooperate with us. The bullies don't change their ways, they just find more soft targets they can bully.
No matter how you deal with your situation, I hope it works out for you.
Thanks,
Jack