Depends on which state you are in but many states have a law that anyone 16 or younger must wear a helmet on a bicycle.
State Motorcycle and Bicycle Helmet Laws
www.ghsa.org/.../stateinfo/laws/h
I'm going bike riding on Sunday, but I don't have a helmet. Would I get "in trouble" for not wearing a helmet? Thanks!
If there is a helmet law where you intend to ride .. Then yep, you bet, it's entirely possible.