In nearly every incorporated area it's illegal to discharge a weapon except under very specific circumstances, and that means pellet guns too. So you can't shoot any wildlife, drones, pets, etc. If you're in a designated firing range, OK. If you're under attack, maybe depending on the jurisdiction and if you're inside or outside. Even in stand your ground states if you're chasing someone (and not in law enforcement) and they're outside you are not being threatened so you'd lose your stand your ground defense.
Odds are shooting down a drone would get in trouble on all sorts of fronts, not counting pissing off the neighbor who's house it crashes into. The good news is if that neighbor comes over and tries to beat the crap out of you, you might be able to shoot him.