But it is not a “loophole.” It is federal law, and it applies everywhere in US territory all the time.

You are stating it as if a gun show is some magical arena of anarchy where law does not apply.

You may sell a SINGLE gun, or even a small handful, if they are personal property. The moment the ATF determines you’ve engaged in “business” rather than “disposing of personal property,” you are a FELON.

And fun fact: There are ATF agents at every gun show. Compliance with the law tends to be a lot higher than elsewhere.