Certainly demonstrating competence and possessing knowledge of the legalities of using deadly force is not too much to ask of someone who wishes to carry a deadly weapon in public.
We require motorists to demonstrate the ability to control an automobile before they're licensed to drive solo. As I recall, they also have to know the rules of the road.
Ex-military or ex-LEO should be considered competent based on their experience. and training.
There are a lot of folks I've seen who give me pause when I consider letting them out in public at all, to say nothing of their being in command of a 2000 pound vehicle or a pistol. For my own well-being and that of my loved ones, I'd like to know that they have at least heard a few basic firearm safety rules, and that they know what the long pedal does.