This is an ongoing issue here in Oregon.On the Trask river there is a guy who think he can stop you from anchoring in the river and has posted signs to that extent. He owns Tillamook Sporting Goods also and once he drove his Mercedes up to the edge of the river and tried to make some guys anchored there leave. My impression is the high water mark is state owned and anglers can use that but you cannot cross private property to access it without permission.