It seems some folks in this debate, have missed one scenario, in all of this. So, let me illuminate!
If I was a prosecuting attorney, for an Az municipality, I would assume upon investigating a crime committed with a firearm, and tracked it back to the seller, who presented a multitude of documentation of the sale, because he didn't like the looks or attitude of the buyer.
I would come to the conclusion that the seller thought the buyer was a questionable buyer at best, and a a prohibited possessor at worst.
Annnd,... since knowledge of an individual being a prohibited possessor is the only restriction to a firearm sale in Arizona,... any actions taken by a seller, that would be evidence to them having knowledge that the buyer was questionable, at the very least,... would give me grounds to prosecute for, selling to a prohibited possessor.
Might be a tough row to hoe,... but, the cost wouldn't be on the prosecutor,... if you get my drift!