so is a drone in navigable airspace?
Depends on the altitude. IIRC, that same law, as someone else mentioned, said you owned the air-space up to 83 feet (weird number, I'd like to see what it was based on). But that from 83 feet up, the government considered it a public right-of-way, but set lower limits on aircraft depending on distance from the airport given safety concerns. RC planes/copters and drones are certainly in a grey area. I don't really care, I think they're neat, but don't want them directly over my property at an altitude lower than what the tallest structures in my area are (cell towers/trees/power or light poles).
Where we used to live, we'd get hot-air balloons all over the place, they rarely got close enough to hit the house, but a few came over lower than 100'. We lived in an area where there was enough space for them to take off and land.
We didn't care, as we were quite certain our little abode was not high on their list of photogenic objects.