Nomercy448

It's a bit of a loophole, but the way it works out is that you are able to sell it, but the purchaser is only allowed to buy longguns, private sale or via FFL, from states which their residency state allows. For all states I'm aware of, that's their own state, and those contiguous to it. For handguns, it's illegal in all states that I'm aware of to purchase handguns out of state without transferring to an FFL within your own state, which inevitably means you must have it shipped from a local FFL in the seller state.

So technically there are no stipulations to whom a person can sell a firearm. For instance, the seller is not obligated to confirm state of residency, or criminal background, etc. However, the liability is steep on the buyer - Buyers have many stipulations controlling their ability to purchase firearms. So if a felon crosses state lines to buy a pistol, the seller (in states that don't require 4473's for private transfers) isn't burdened to cease the sale under the law, but the purchasers are twice prohibited from buying it.

Of course, if your state does require 4473's be processed through an FFL for private party to party sales, then you have that liability. That's literally the ONLY control I have ever heard of for a seller - i.e. that law would state something along the lines that the seller of a firearm must conduct the transfer via a legal FFL holder. At which point, all other liabilities for sale are transfered to the FFL holder and the buying party.