Those who favor more restrictive laws for gun purchases often trap themselves in static modes of thinking. The disarmament lobby is fond of quoting statistics showing how often guns from shows are used in crime. Currently, many criminals attempt to purchase guns even at stores, simply because they have a chance of slipping through the background check, and to date little effort has been made to prosecute the unlawful attempt to purchase a gun. Thus, a person with criminal intent can attempt to purchase a gun at a store and bear essentially zero risk. The worst thing that now happens to a criminal who fails a background check is that he or she has to purchase a gun elsewhere.
Many criminals undoubtedly seek to buy a gun from a less-regulated gun show.
However, there is no reason to believe that criminals will simply give up their search for a gun if background checks are mandated for all purchases at gun shows. Instead, the criminals will purchase their guns from unregulated private sellers outside of gun shows or they will steal the guns or buy them on the black-market. If the regulations are carried far enough, garage gun manufacturing will become common place. Of course, some criminals are a few grains short of a full load, so they might still attempt to pass a background check even if doing so starts to carry criminal penalties. But these are not the criminals as likely to have the intelligence to carry out their plans anyway.