1. The majority of crime guns come from straw purchasers or a stolen per the DOJ, this universal background checks wouldn't actually reduce crime.
http://www.nraila.org/media/10883516...olicy-memo.pdf
2. Even those who are denied during current background checks, where the majority of guns are already purchased, are not prosecuted. It is a felony to lie on federal form 4473. In 2010 of the 76k denials from the background check only 62 per prosecuted.
https://www.ncjrs.gov/pdffiles1/bjs/grants/239272.pdf...