You are correct in part. Much or all of the Grand Canyon is off limits to drone flying but none of this discussion was about a National Park. The attached file shows the FAA areas around the Canyon that do not allow flight. The National Parks are designated no-fly however it is not the Park Rules, per se that designate it, it is the FAA through a law passed in 2014 that puts them off limits. In the case I've been discussing above, the FAA has no rule against flying over the State Park, therefore I can launch from anywhere outside the state park (since it is not FAA forbidden) and fly over the state park IN SPITE of the state park policy forbidding drones. Their no-drone policy can only apply to launching from state park land. The air above is controlled by the FAA. If our state park was covered in a Restricted Operations area like the Grand Canyon then I would be forbidden to fly there too. All airspace is controlled by the FAA. National Parks are all off limits as far as I know and so designated by the FAA maps. B4UFLY is a good place to check FAA airspace rules and any Park or other area should be checked for their rules regarding whether or not it is permissible to fly your drone from their land.