Besides the obvious (don't go around shooting random people, airsoft on public or private property without permission, painting the orange tip of the gun, etc.), no.
Yes, airsoft guns are legal in TN.
yes airsoft guns are legal in OHIO
Yes, airsoft guns are legal in Canada.
Usually airsoft guns aren't allowed in public places
Yes
Yes
Yes
Yes they are.
Yes, they are.
18 in the USA
Yes, i'm 14 and i own 4 airsoft guns.. As long as its on your property and not like in a city
Yes, they're legal in all states.
I don't know about Canadian airsoft stores, but I know that most airsoft in North America sell Canadian-legal airsoft guns.