Question: I observed a drone hover over our back yard, so close I could see the markings on the body. I yelled for it to leave (foolishly, of course the operator couldn't hear me). When it stayed put, I shot it down with my shotgun. Have I done anything wrong?
Answer: You might be criminally liable for destroying property, or civilly liable for the cost of replacing the drone…or maybe not.
By law in all states, landowners are allowed to use reasonable force to eject trespassers. This includes not only persons, but tree branches that overhang a boundary line. The question you've presented is whether the drone was a trespasser, and if so, whether shooting it down constituted a reasonable response.
Determining whether the drone was trespassing requires you to know whether your state or locality has passed any laws that define protected air space above your property, known as the "buffer zone" that all owners are entitled to. If you're lucky, you'll find an applicable statute or ordinance that proscribes drone use below a certain ceiling, such as three hundred feet. But if no such laws apply, you'll need to figure out whether the drone was flying at a height that that limited your full enjoyment of your land and your ability to exploit it. (That's the U.S. Supreme Court's definition of the protected "buffer zone." For more information on drones and trespassing, see our article, "When a Drone Flies Over My House, Is It Trespassing?") A court case in your state might give you guidance, but in its absence, you'll be guessing.
Assuming you can establish that the drone was trespassing, the next question is whether you used reasonable force to eject it. That's anyone's guess, as there are no reported cases at this time to guide us in making that determination.
Finally, you'll need to know whether the drone was operating pursuant to a permit issued by the FAA, or not. According to regulations issued by the FAA, effective in August 2016, it is unlawful to operate a drone for commercial purposes without an FAA exemption or certificate. If the drone was permitted, will this permit trump any applicable state or local laws regarding the buffer zone? That's hard to know, though the FAA itself has cautioned that the drone pilot may need to comply with applicable trespassing laws.