The Bureau of Alcohol, Tobacco, Firearms and Explosives is in charge of determining whether a gun model is legal, but the agency won’t say much about its criteria.
Despite overseeing an industry that includes machine guns and other deadly weapons, ATF regulations for the manufacture of weapons are often unclear, leading to reliance on a secretive system by which firearms manufacturers can submit proposed weapons for testing and find out one at a time whether they comply with the law, critics say...
http://www.washingtontimes.com/news/2012/jan/2/gun-makers-baffled-by-atf-criteria/
