I had an 01 FFL back in the mid to late 90's. The BATF agent who came to my home to interview me told me he didn't want me selling at gun shows. He was VERY fixated on gun shows. He didn't say it was against the law, he just warned me in an intimidating manner not to do it. I researched, and found that with a 01 FFL it was perfectly legal for me to sell at gun shows. However, as I had not intention of buying or selling firearms as a business, I never sold at gun shows or anywhere. I just wanted to do a little gunsmithing on the side, and wanted to make sure it was legal. The attitude of that BATF agent has always stuck with me though.