UPIN – Universal Personal Identification Number
I believe it was set up for folks that have problems passing an NICS background check, but do not really have an issue that prohibits buying a firearm. With the UPIN you include it on the form 4473 to avoid denials.
A major source of objection to a free economy is precisely that it ... gives people what they want instead of what a particular group thinks they ought to want. Underlying most arguments against the free market is a lack of belief in freedom itself.
- Milton Friedman