Department of the Treasury Study on the Sporting Suitability of Modified Semiautomatic Assault Rifles [open pdf - 3MB]
"On November 14, 1997, the President and the Secretary of the Treasury ordered a review of the importation of certain modified versions of semiautomatic assault rifles into the United States. The decision to conduct this review stemmed in part from concerns expressed by members of Congress and others that the rifles being imported were essentially the same as semiautomatic assault rifles previously determined to be nonimportable in a 1989 decision by the Bureau of Alcohol, Tobacco and Firearms (ATF). The decision also stemmed from the fact that nearly 10 years had passed since the last comprehensive review of the importation of rifles, and many new rifles had been developed during this time. Under 18 U.S.C. section 925(d)(3), the Secretary shall approve applications for importation only when the firearms are generally recognized as particularly suitable for or readily adaptable to sporting purposes (the 'sporting purposes test'). In 1989, ATF denied applications to import a series of semiautomatic versions of automatic-fire military assault rifles. When ATF examined these semiautomatic assault rifles, it found that the rifles, while no longer machineguns, still had a military configuration that was designed for killing and disabling the enemy and that distinguished the rifles from traditional sporting rifles. This distinctively military configuration served as the basis for ATF's finding that the rifles were not considered sporting rifles under the statute."
Bureau of Alcohol, Tobacco, Firearms, and Explosives: http://www.atf.gov/