CBS Philadelphia reports that, “[a] New Jersey man was arrested” — for “Possession of a Weapon for an Unlawful Purpose and Criminal Mischief” — “after police say he shot down a neighbor’s remote control drone.” The drone was apparently over his neighbor’s land, but what if it had been over the shooter’s land? Would it be illegal property damage — or lawful defense against trespass?

Even nondeadly force against people is allowed to prevent trespass, if it’s “reasonable”; as the Restatement (Second) of Torts puts it:

An actor is privileged to use reasonable [nondeadly] force, … to prevent or terminate another’s intrusion upon the actor’s land …, if the actor reasonably believes that the intrusion can be prevented or terminated only by the force used, and … the actor reasonably believes that a request [to desist] will be useless or that substantial harm will be done before it can be made.

It seems then that force exerted only on objects would likewise be allowed in such situations if it’s “reasonable.” Indeed, a separate provision specifically says that reasonable force that may damage property is sometimes allowed to protect one’s land:

[O]ne is privileged to commit an act which would otherwise be a trespass to a chattel … if the act … is reasonably believed to be … necessary to protect the actor’s land or chattels or his possession of them, and the harm inflicted is not unreasonable as compared with the harm threatened.

And an overflight may be a trespass to land — and thus a potential justification for the use of nondeadly force — if the aircraft “enters into the immediate reaches of the air space next to the land, and … interferes substantially with the other’s use and enjoyment of his land.” And criminal law rules are generally similar; indeed, the relevant New Jersey statute provides, in relevant part, that “Conduct involving the appropriation, seizure or destruction of, damage to, intrusion on, or interference with, property is justifiable under circumstances which would establish a defense of privilege in a civil action.”

Yet is force that damages a potentially quite valuable piece of machinery reasonable? Is the interference of an overflying drone with one’s use and enjoyment of land “substantial,” and should shooting down the drone be seen as “necessary to protect the actor’s land … or his possession of [the land]”? The chief threat wouldn’t be of physical damage to land, but of interference with privacy — should that count for defense-of-property purposes? What if the drone weren’t over the shooter’s land, but was instead over a public street, but apparently photographing into the shooter’s home (if one can tell such a thing) or into the shooter’s fenced-off swimming pool deck? Would the shooter still have a defense for using force purely to protect privacy (e.g., to prevent the tort of intrusion upon seclusion), even in the absence of a trespass)?

Very interesting questions, which I thought I’d just flag here now. (Note that the Restatement is a distillation of the common-law rules, not a statute; the case law is thus free to evolve by analogy, as incidents involving drones arise.) I’m delighted to say, though, that Prof. Michael Froomkin (Miami) will be guest-blogging about these very issues today or Friday; he is the co-author of a new article that is all about Self-Defense Against Robots.

Thanks to my colleague Richard Re for the pointer.