The mere act of trying to buy a firearm by a prohibited person is a crime. Supposedly there are many thousand denials every years and some of them are prohibited felons. If your law works so well, why are there no more than a handful of prosecutions for these attempted purchases?
The law is near 100% effective. The failure of the feds to act on these known violators is an exercise of prosecutorial discretion. Obviously, most of them will attempt to get them somewhere else. The fact that they're not prosecuted, could reflect on the nature of the disqualification. I wouldn't like to see those disqualified by Lautenberg, or mental illness jailed, just the scumbags. If they're being ignored, then it's clear they're not interested in preventing scumbags from continuing on preying on the public. So, the code dinks and other grabbers should be ranting on the feds, not in the legislatures to disarm their fellow citizens.