The U.S. has long had two distinct applications of federal gun law. One applies to people who shop at federally licensed gun dealers: They must pass a background check before purchasing a firearm. The other is for those who arrange a private sale from an unlicensed seller, via the internet or at a gun show: They are under no obligation to prove they are legally qualified to make their purchase. A 2015 survey found that more than one-fifth of Americans who obtained a gun in the two years prior to the study did so without a background check.
The disparity is absurd, especially when you consider how often people who are legally barred from buying guns try to buy them. Since 1994, more than 3.5 million attempted gun purchases have been denied, including efforts by convicted felons, domestic abusers and others.