I've had this happen twice.
Once was at a gun show, I was selling off one of the last Saxony Police import H&K P7s from a few years back, and a younger guy came up to me and wanted to buy it, but he wanted to buy it without even looking at it, and it seemed apparent he didn't know what it was he was looking to buy. He wouldn't look me in the eye, and didn't attempt to negotiate the price at all. I asked him to see his driver's license and permit to carry, and he immediately said he'd forgotten them at home, but that he'd give me more money if I sold it to him anyway.
PASS. Sold it to another private party at the same gun show who was more than willing to talk my ear off about wartime production Mausers and old H&K pistols. Considered reporting the first guy to the police running show security, but he skedaddled at high speed before I could find one.
Second time was off of Armslist, selling a Beretta 92A1. Guy seemed fairly normal at first, but wanted to meet to inspect the gun at his girlfriend's place of business, which was pretty local to me. No problem.
So I get there, and he's a little twitchy, but hey, that's not a crime. He's got some Tommy Tactical black chest rig and nylon duty belt setup on a counter and tells me he needs it as a new 'duty gun' for his work for 'Homeland Security.' I even get the line that what he does for DHS is top secret, and he'd have to kill me if he told me. There's no gun in the duty belt holster, all of the pouches are empty, and it's not set up like an actual LE duty belt. Uh huh. Well, I go into my usual spiel about 'Let's see your driver's license and permit to carry...' and
surprise,
surprise, this guy also left them at home, this time in his 'bulletproof vest.'
So I tell him, OK, you must live pretty close by, just go get it, and we'll meet up again later tonight or whatever.
When I get back to my house, I have a lengthy e-mail saying that he doesn't feel comfortable buying from
me, because I don't know that 'law enforcement officers don't need a permit to carry to buy a gun.'
Sure, boss, whatever. You're not a cop. I hope you know that as well as I do. Even if you were, there's no exemption to the state requirement of a permit to purchase or a permit to carry a pistol in order to buy handguns or 'assault weapons' from a dealer, a requirement that I have always made for private sales as well. PASS.
I believe the key to determining whether a sale should go forward is based solely on behavior. I've never judged a buyer by their appearance, their car, their tattoos, or whether or not I like the cut of their jib. Only by what they say and what they do.
Generally speaking, the lawful acceptance of a lawful offer constitutes a contract. Contracts can be terminated, but the rights and obligations of the parties involved vary according to local laws, circumstances, and the terms of the contract.
It is not a good idea to enter into a "deal" and then decide to get out of it, unless you know what you are doing.
A person may refuse to sell to just about anyone for just about any reason, but there are exceptions. But once a lawful sale has been agreed upon, "cancelling the deal" just might not be as simple as it may sound.
If you actually have a "deal" and you decide that you want to "cancel" it, you should have made it your business to know in advance what that would entail in your jurisdiction , and what obligations you might have.
Isn't the solution to this to not agree to a deal until you meet in person? This protects the buyer and the seller and is how I've always done it. I haven't agreed to a lawful sale, I've simply agreed to meet you so that you can see the gun I am selling is as described and I can see that you're not a prohibited person, both of which are preconditions to selling. If both of us are happy with the results of the meeting,
then we have a deal.
