As a practical issue for the RKBA - the issue of lack of training is brought up every time we have a debate about campus carry.
I testified in front of the TX House on our concealed carry bill. My two cents went well. However, the anticarry folks kept bringing up that casual carriers may be ineffective or at worst dangerous.
That doesn't apply to me as I've trained a touch. I have had anticarry folks at work say they would be ok with me carrying as they know I have the background, blah, blah but fear the old cowboy coot with little competency or green behind the ears frat boy.
The argument can be negated by it's there and I share it as a practical matter in debate.
So Mr. Shooter - you want to carry a concealed weapon and perhaps by a good samaritan? Might you tell us how you have trained for such?
-- I have no training because the 2nd Amend. - blah, blah.
Now -it's a double edged sword because if Mr. Shooter gets into one of those famous good shots that somehow ends in court (how did that happen?), a training regime may be brought up against you - esp. if it as some of those neat quotes in class - like have a plan to shoot everyone you see, etc.