Many believe that unregulated, haphazard firearm sales are occurring by the millions, utilizing the so-called "gun show loophole." Based on my experiences, I do not believe this is the case.
While private sales do occur, I believe most are conducted in a thoughtful, reasonable manner. In every private transaction to which I have been a party, the buyer produced a valid concealed pistol license and identification.
Just because a transaction does not include a national instant criminal background check does not mean people are circumventing responsibility.
For other private transactions, I propose changing the existing law (RCW 9.41.080), which makes it illegal to deliver a firearm to someone who you know or have reasonable cause to believe is ineligible to possess a firearm, to make it illegal to transfer a firearm to someone ineligible to possess a firearm and would not pass a NICS check if conducted at the time of transfer.
Make it an absolute defense if the transferee produces a concealed pistol license, law enforcement ID, collector's license, or completed background check (allow local sheriffs to run them).
This law would not "require" background checks, but would place greater responsibility on the transferor, achieving the desired results while allowing leniency when appropriate.