For a long time, MO had a law that required individuals to obtain a 'permit to purchase' (from the high sheriff) any handgun, regardless of whether it was being purchased from a dealer or individual.
It was soundly ignored by folks who knew each other, knew the other guy wasn't a nut/robber/doper, etc. The law existed for decades and I saw exactly two people prosecuted for violating it. Both were suspects in homicides.
“Nine-tenths of tactics are certain, and taught in books: but the irrational tenth is like the kingfisher flashing across the pool, and that is the test of generals. It can only be ensured by instinct, sharpened by thought practicing the stroke so often that at the crisis it is as natural as a reflex.” ~ T. E. Lawrence