Flying drones have been falling foul of FAA regulations but now they face a new threat - angry shotgun-wielding neighbours.

A California court has fined Brett McBay $850 for shooting his neighbor's home-built drone out of the sky with a 12-gauge shotgun after he claimed it was spying on him.

Eric Joe was flying his homemade hexacopter drone in his parent's backyard in Modesto, Calif., in November 2014 when it was struck by shotgun fire from nearby walnut trees. 

"When I went out to go find it, I saw him come out, shotgun in hand," Joe told Ars Technica. Joe claims McBay shot the drone down because he thought it was CIA surveillance vehicle. When the two men could not agree on a fee to compensate for the broken drone, Joe brought the case before the California small claims courts.

McBay claimed the drone was flying over his property and he was within his rights to shoot, despite GPS data provided by Joe showing that the machine was hovering over a walnut orchard owned by his parents, not McBay's property, when it was brought down.

However, the location of the drone didn't actually matter. "Court finds that Mr. McBay acted unreasonably in having his son shoot the drone down regardless of whether it was over his property or not," the Stanislaus County Court Small Claims Division found as it handed out the $850 fine to McBay.

Just as McBay refused to pay the $700 initially requested from the drone maker, he still hasn't paid the court damages. Joe has said that if he is not paid he will pursue further legal action.

It's not the first case of a drone being shot down. There was a similar incident in New Jersey last September when a man was arrested and charged with "possession of a weapon for an unlawful purpose and criminal mischief" for shooting down his neighbors drone.

Existing federal law and judicial rulings make it clear property owners do not enjoy unlimited privacy rights to their airspace and even if they did there are additional laws that prevent the firing of shotguns in urban areas. So unless you want to find yourself in front of a judge, it's probably best if you keep your shotgun locked up.