Considering someone would have had to surreptitiously home-brew a jet pack rivalling the Yves Rossi Jetman in order to get to that altitude, I would not be surprised if this turned out to be a balloon "dressed up" to look like a person with a jetpack.
One would think that there would be higher fines for this sort of misbehavior.
As it turns out, you can't just make up laws just because someone did something unsafe for the purpose of punishing said person
Isn't this the difference between common law and civil law? That under common law the existing body of written laws doesn't need to cover every eventuality, because equitable principles and "natural" law can be applied when necessary
You can absolutely pass laws to punish the next person who tries it, though.