I wouldnt be so much worried about the aircraft skin, id be much more worried about the bullet taking out controls, operating mechanisms or pilots. Redundancy can only prepare you for so much at 30k feet.
I dont remember the exact case number but try to find the two guys from Kansas who built their own after they passed similar legislation. Short version is, the state hid in the closest while the feds drug them guys over the coals.
That is my thoughts. How is it actually enforceable without running a sting operation? Drug deals happen every second and few of them are ever caught and even then it takes someone being undercover most time to catch them in the act.
Maybe we should just not choose between 2 people who don't give a rats ass about the normal joe. The whole system is completely warped from what it was originally designed to achieve.