Mesh
Apart from the legal battles of implementing this, what's to stop someone from doing this:
"If one comes over my field I'll shoot it out of the sky a grab the goodies (as well as the drone)!!" 
This is surely going to open up a can of worms.....
There are laws against theft and destruction of property. Even if the property is within your airspace, you are not automatically justified in seizing, damaging or destroying it. You can not make a valid claim to own the contents of an armored car that uses your driveway to turn around.
And there are definitely limits on the airspace a land owner can claim. By statute the navigable airspace above your property is controlled by the United States, and you cannot impede travel in that space. If you could show that the invasion of your airspace posed a clear danger or resulted in such a deterioration of your enjoyment and utilization of it as to render it unusable you might be able to seek redress...but probably not with buckshot.
http://supreme.justia.com...l/us/328/256/case.html