We legally own the property and road entrance, but our neighbor installed an electric wire + sign across it… what can we do?

So, we officially own this property — including the entrance road. It’s clearly on our deed, confirmed by the survey. But the guy who lives across the street (and owns the field next to the stone wall) has decided he’s also the sheriff of the neighborhood. He just installed this electric wire and a big “No Trespassing” sign right across our …