Under 21 but 18 and over you can possess inside vehicle as an extension of home. If you're 18 and military you can get a weapons carry license. The 19 yr old was covered because by ga law he was not a minor and in lawful possession of a firearm inside his vehicle. Without a wcl he can not carry on his person except in certain places which are annotated in OCGA. Law enforcement also cant detain for the sole purpose of identifying whether or not a person has a wcl