Did they shoot the paintballs or just drop them? Unless they flew too low, I really dont see how they broke the regs. I would say its just some over zealous, and jealous, cops that want to charge these guys.
Now if they flew too low and shot the paintballs out of the plane... then well they are screwed, and quite frankly should be.
But what we should have learned from the Duke Lacross case is, that we really should wait for all the facts.