in vermont, where i live, it depends on the TYPE of sign that dtermines if you can go on the trail or not. for example it HAS GOT TO BE a specific color, in this case, yellow. it has to be registered with the county as private. and lastly it has to be a specific sign saying in detail what or whom can not be on the land. so lets recap, yellow is legal, if its any other color you can go on it no matter what the owner says, and if the cops show up show them the sign and then you are asked to leave, not arrested. if it is a home made sign, haha blow it off there is nothing the owner can do. the sign has to be registered every year with the county and i think it cost's around $30 to register, if you do go on the land and see a posted sign get out, check the date, and if its over a year old, nothing anyone can do other than ask you to leave. so now you all know the wacky laws in little ole vermont.