Second Amendment may invalidate ban on opening new gun stores in a California county

[gejohnston]

16. Criminals don't go to gun stores

or gun shows, that was well known among criminologists before the NICS requirement came into being.
http://www.davekopel.org/2A/EncyGunsInAmerSociety/James-D-Wright.htm

Even the prohibition lobby's John Lott says this.

As documented below, survey evidence provides strong evidence
that the gun market is sharply differentiated by the characteristics of
the individual who is seeking a gun. Adults who are entitled to
possess a gun are more likely than not to buy from an FFL. On the
other hand, those who are disqualified by age or criminal history
are most likely to obtain their guns in off-the-books transactions,
often from social connections such as family and acquaintances, or
from “street” sources such as illicit brokers or drug dealers. While
some of these illicit transactions are purchases, they also take a
variety of other forms.

https://d3uwh8jpzww49g.cloudfront.net/sharedmedia/1508093/ccjstudy.pdf

BTW, any violation of the Gun Control Act, including selling without background checks, is up to ten years per gun.