You cant legally (edit: in the USA, at least) shoot at drones even if they are tresspassing.
Well, technically they wouldn't even be tresspassing since FAA owns all airspace, they'd be inside FAA airspace.
Shooting down a drone is treated the same as shooting down a manned aircraft, a felony. (not that they would actually enforce it, but its technically on the books)
Signal jammers are also illegal (again, not that someone would enforce it, but its on the books)
What would likely happens is:
If a rich person shoot down a non-rich person's drone, the drone operator gets punished for "reckless drone flight" slap a huge fine if first offence, potentially jail time for future offences. The illegal act of shooting down a drone would not be enforced.
If a rich person flew a drone to harass a non-rich person, and the non-rich person shoots it down, boom, felony conviction for the person shooting down the drone, zero punishment for the drone operator.
This is how drone issues would be resolved