Handguns are already restricted to age 21 but that still doesn't do anything about the teenagers with stolen guns, although it might help with the idiots who leave their legal guns in a car, which is where most stolen guns were before the theft.
We need to require training and impose harsher penalties for leaving guns in cars without being secured in a case, which is required in many states. People do the legal thing by not taking their gun into a place where it's not allowed, but they do the stupid thing by leaving it where someone can easily steal it. Only in America.
