I couple years ago I decided to do a video of Point Arena light house. Upon arrive at the main gate they had a sign stating drones are restricted from flying on their Point Arena grounds. I parked about fifty yards away from the main gate and launched my drone, filmed the light house and came back and landed. I ranger came out and told me that I just broke the law by flying over their property.
To make a long story short, I asked him to call the nearest FAA office and asked them about airspace restrictions, and that they can definitely keep me from landing on their property, but they can not keep me from overflying it unless the FAA has restricted the airspace.
He summoned a local Sheriff, an that guy was clueless and told the ranger he needed to talk to the people at the airport regarding such flights
I normally don't challenge authority, but sometimes if you know you are right, then it is worth it. I guess you just need to weight the costs and potential problems.
It seems to me when local authorities feel they may be stepping on federal law they become a little more careful.