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.
I'm inclined to think if a man hasn't gotten his point across in 4912 attempts, 4913 probably isn't going to do it.