What deeply troubles me about the current debate about civilian drones is the rush to legislation.
There has been absolutely no showing that our common law courts will lack the ability to develop appropriate remedies if a drone is used to invade privacy.
The tort is Intrusion into Seclusion, based on Section 652 of the Restatement of Torts (Second) 1977. A link to the text.
Several commenters can be found with The Google, but this one seemed the most useful start.
Elements of an Intrusion Claim | Digital Media Law Project: