Well if the LEO had reasonable suspicion to believe that you were carrying while underage then he could stop you ask for you ID. The same could be said if he had reasonable suspicion that you were a felon carrying a gun then he could stop you. But just having a hunch that you are underage or might be a felon is not probable cause for a stop. The responsibility is on the LEO to show that we ARE NOT of legal age to carry - not the other way around. Innocent until proven guilty kind of thing. IANAL.