I agree, legal action is the way to go and it works. My family owns some nice deer and turkey hunting land and granted my parents' portion of the division is only about 22 acres, people still try to get on it every year. They have pressed trespassing charges on a few parties that have been caught (the majority by gathering tag numbers of vehicles parked on the roadside boundary of the land) and so far there have been no repeat offenders. Just something for you to throw around the noggin.