Don't make the assumption that everything air-powered is nonlethal. Indeed in history we find:
"In the late 1700's, powerful pneumatic guns even found their way into the ranks of the military. The Austrian Army had an entire regiment armed with .44 caliber repeating air rifles. All surviving accounts indicate that the Austrians used those airguns with deadly effectiveness against Napoleon's army. So feared, any Austrian soldier captured with an air rifle was summarily executed as an assassin!"
(http://www.airguns.net/general_airgun_history.php)
Because the terrorists had their AK-47s legally. Wouldn't it just be easier to put up a sign "no entry to terrorists"? Then they'd have to just shrug and go away.
Well of course they are. Everyone knows that shotguns purchased in stores are much more dangerous than AK-47s purchased from a smuggler in a back alley.
