Looks like the police has the right at least to 400 feet above the property.

http://en.wikipedia.org/wiki/Florida_v._Riley

However this was partially based that overflights by helicopters at this height was not rare. I would likely be rare for drones. Also I believe this was a liberal court, it might be a differant issue for a conservative court, and might be differant for a privately owned drone taking, say for example, real estate photo's.