I remember seeing a sign on private property warning about a cop spot 1/2 mile ahead. It was either in NE TX or SE OK. I asked about it and the guy who put it up would move it to keep up with where the cops would hideout. He got legal permission from the property owners and there was nothing the cops could do about it.
I don’t think that would be allowed in the Pelican State. A lot of the traffic in the area of the speed trap is from out of State.