Still can far as I know. Just not in a school zone. Or a mall, probably. Right?
Mac.
Depends on your local law enforcement and prosecutors.
I have seen occasional article on problems because the are deemed dangerous, some where is is a discharge of a firearm (comes into play for those using hairspray, lighter fluid, ether, etc.), or even an actual cannon because of its large bore. With good representation you may get off, but what about the time and expense to prove you are right?
The neat thing about this knowledge we gained growing up is its value. Isn't it this same primitive technology that is giving our armed forces the challenges in Iraq? Imagine if we found our selves in trouble over here and didn't have this experience form "playing around?" And the Brady Bunch is afraid of my plinking guns. When are they coming after my old pop cans, lighter fluid, tennis balls and wood matches?