“You can’t invade someone’s privacy by looking at something that’s clearly visible from another property. It wasn’t private to begin with.”
The reasonable expectation of privacy is already protected in law. This can even include persons visible through open windows from outside the property line, but I suspect that you’d need to prove intent. A telescope aimed at a window could convince a jury.
Drones photographing private property that is otherwise not visible from the outside are undoubtedly going to get drawn into the argument of what constitutes a reasonable expectation of privacy and what is a criminal invasion of that right.
“Drones photographing private property that is otherwise not visible from the outside”
...is also visible on Google Earth.