The answer to both your concerns about not letting idiots have guns contrasted with the constitutionality of requiring training for the exercise of a right is to start including gun safety in the curriculum at grade school. That way, everyone knows how to handle a gun, so even if by some twist of fate, an immigrant or someone like that manages to attain adulthood without being well-versed in firearms safety, he or she is surrounded by a population who DO know about gun safety, and can show them the way. You don't *need* to be able to read or write to practice free speech, but it sure helps. Same should go for guns, IMHO.