Faster than a speeding face plant!
The one problem is that i see something like this getting quite out of hand. Maybe in a situation with a guy who is flying around the airport repeatedly and the airport allows other hobbyists to knock him out of the sky. but otherwise even if it seems like a a quad is breaking the law you can still be liable for hitting his drone.
However, any government solution will also get quite out of hand, be far more expensive, less effective, and include home raids and guns. I say, let the privateer market figure it out. We'll be safer and it will cost less in the long run.
"I prefer dangerous freedom over peaceful slavery" -Jefferson