THE NRA is the ATF'S biggest enemy: The story

The NRA also scored a long-lasting victory in the 1986 Firearms Owners Protection Act, which eased rules so individuals could sell weapons from private collections without possessing a federal firearms license.
That redefinition of what it meant to be "engaged in the business" of selling firearms opened up what came to be known as the "gun-show loophole," in which private sellers circumvent paperwork and background-check requirements imposed on licensees. To this day it "handcuffs the ATF," as gun-control advocate Dennis Henigan put it.


http://www.sfgate.com/nation/article/How-the-NRA-became-ATF-s-biggest-enemy-4950703.php