The doctrine originally applied to vehicle stops for traffic violations. Courts held that anything in plain view of the public does not require a warrant for officers to see.

Whether that doctrine applies to air views of private property is part of the problem that the courts have not yet decided.

One argument is that people fence their property to obtain privacy, and no government official should be allowed to view anything inside that fence without a warrant. The land owner also owns the airspace above his land, so that drone intrusion would be a trespass of his air space. And of course, stalking is prohibited by law.

Legally, it is obvious that the government has no right to intrude on the privacy of land owners without probable cause and a search warrant.

And probable cause must relate specifically to each land owner below the drone camera, not some third party whose actions may or may not justify a search warrant. So the real question is whether the government shall obey the law, or not, and if they fly drones over private property without a warrant, then they have violated the law.