There's an old thread someone in CE&P or HT that has a discussion between Kuhlindahr and me about the NRA that we knew growing up.  A lot of kids in the US learn about guns from family members but until the 1980s, the NRA was known for conducting gun safety classes for kids and adults.  
That history, 
got them tax exempt status under IRS 1(c)(4).  On paper, the NRA is a "social welfare organization".
IRS 501(c)(4) organizations are allowed to lobby government.  Donations made to 501(c)(4) orgs are not tax-deductible.  But the income for 501(c)(4) are tax exempt, as long as most of their spending is made toward "social welfare".
If I get a chance, I'll have to find the thread with the discussion with Kuhlindahr - about how the NRA changed over the past 30 years and how they've diverted member dues to pay exorbitant executive salaries for people like Wayne LaPierre.  That discussion was probably 2-3 years ago, so it's good to see that the gig is about to be up for Mr LaPierre and the buying off of politicians.  
LaPierre is in deep shit.  The NRA is in even deeper shit.  They're about to lose their tax-exempt status unless Congress bails them out.