Actually, the AG may not make the determination of what sporting purposes is. It could very well be some ATF flunkie.
Here is 18 U.S.C. 925(d)(3):
(3) is of a type that does not fall within the definition of a firearm as defined in section 5845(a) of the Internal Revenue Code of 1986 and is generally recognized as particularly suitable for or readily adaptable to sporting purposes, excluding surplus military firearms, except in any case where the Attorney General has not authorized the importation of the firearm pursuant to this paragraph, it shall be unlawful to import any frame, receiver, or barrel of such firearm which would be prohibited if assembled
Basically, under the code it looks like the AG can ban certain firearm, but not parts for firearms. Either way, I'm still not a Gonzales fan knowing what his stand is on the 2nd Amendment.
"recognized as particularly suitable for or readily adaptable to sporting purposes, excluding surplus military firearms,"
So I guess that means that we can't claim that the parts are needed for maintaining competition firearms such as used in the Heavy Metal class at the 3 gun matches?