If one of these things is flying over YOUR PROPERTY are you allowed to blast it out of the sky?
There is debate as to the ownership of airspace below 500 ft. Which is the minimum height that aircraft can flow over populated areas. The fact that they restrict it to below 400 ft. means that it is within the airspace that normally would be covered by property rights.
Now, the reason I chose an Estes model rocket in my example is that it is legal to shoot them in the city. They travel at upwards of 1000ft a sec and can reach altitudes of over 3000ft. They require no notification or permission to fire. Thus if one of them happens into the area over your back yard and you happen to hit it with the rocket then there is not much you can do. Then again, my guess would be that the person flying it would freak a bit, even on a close call and at 400ft there is a chance of it crashing just from his reaction throwing it off course.
I would also note that Texas is a very strong property rights state. The police can not just walk onto your back yard and retrieve the crashed aircraft. They do have to ask permission. So, I would not be surprised if they loose a few.