When I go to buy a gun and give info, etc. who OK's the purchase?

And who approves the sale of weapons between private citizens?

I probably could go around and get a gun, origin kinda sketchy, that I could theoretically carry all around the U.S. in my car, and unless I do something stupid or illegal, no one would be the wiser.

It happens all the time and to tweak a law like that is a little like the barn door closing after someone shot my cow in the pasture.

Soemthing good, like a steak, may come of it, but what protected my cow before that?

And yes, I should have fixed that door!