Trespassing isn't a criminal offense where I live. If you leave when asked by the land owner the worst they can really do is try and charge for damages which they have to prove. Of course you don't have to tell them who you are either and if you are leaving when asked the police will laugh at them.

There are a few exceptions like military bases and railways, but otherwise its a civil mater and the police don't care unless someone is refusing to leave when you have asked them to.