Second Circuit Court of Appeals
http://www-2.cs.cmu.edu/afs/cs.cmu.edu/user/wbardwel/public/nfalist/thompson_center_v_us.txtWhat this appears to say is that TC orriginally discussed the carbine kit with BATF who seemed to say that it was ok to go from pistol to rifle. After TC started marketing it, the BATF appeared to have a change of heart and said that once it became a rifle, it couldn't go back. TC had paid the taxes, and then sought a refund for whatever they were doing... they went to trial and the court agreed with the ATF. They appealed with 2nd Circuit, and the decision was reversed.
The following link I haven't read carefully... but it did contain this item
http://www-2.cs.cmu.edu/afs/cs/user/wbardwel/public/nfalist/us_v_tcenter_br1.txt A retired BATF expert examined a complete Contender pistol and
a complete Contender carbine. It took him over 10 minutes to
remove and assemble parts on these guns in such a way as to
simulate the time it would take to convert a pistol into a carbine
using a carbine kit. (C.A. App. 48.)
Any rifle or shotgun barrel is capable of being readily made
into a short-barrel NFA firearm with a hacksaw. A 21" Contender
carbine barrel can be cut off in 25 seconds with a common hacksaw.
(C.A. App. 103-104.) Moreover, a complete Contender pistol and a
complete Contender carbine are capable of having parts exchanged to
make an NFA firearm, but BATF concedes that these items do not
constitute a short barrel rifle. (Pet. App. 3a, 21a.)Basically the gist from the above links is, don't configure it as a rifle with a <16" barrel.
The next case is from the 10th circuit.
http://caselaw.lp.findlaw.com/cgi-bin/getcase.pl?court=11th&navby=case&no=978425manIt is a little more convoluded because it involves a criminal, an AR15 upper and lower (seperate) with a 14" barrel and a short barrelled shotgun.
This case does discuss the previous case.
One thing it says is that the previous decision specifically applied to the TC kits...
In Thompson/Center, a plurality of three Justices ultimately concluded that it was ambiguous whether Thompson/Center Arms had "made" a short-barreled rifle for purposes of the NFA by packaging together the pistol and the parts kit. Id. at 518, 112 S.Ct. 2102. In the course of reaching this conclusion, the plurality focused on the NFA's definition of "make" in 26 U.S.C. ยง 5845(i). 8 Even though the plurality decided that the definition of "make" was ambiguous as applied to the specific combination of parts packaged by Thompson/Center Arms, the plurality recognized that the definition clearly "cover more than final assembly" of a "firearm" and that " some disassembled aggregation of parts must be included." Id. at 510, 112 S.Ct. 2102 (emphasis supplied). Moreover, the plurality recognized two factual situations in which, under the NFA's definition of "make," packaging together unassembled parts would clearly constitute "making" a "firearm." Id. at 510-12, 112 S.Ct. 2102.Mostly this case complains that the 1991 case isn't at all satisfying... at least for generally application to the problem of guns that have many parts and configurations.
Finally, here is a US Supreme Court appeal in 1992.
http://caselaw.lp.findlaw.com/cgi-bin/getcase.pl?navby=case&court=us&vol=504&page=512This case upholds the first. You actually have to assemble it for it to be illegal... taking the second case into account, this seems to specifically apply to TC pistols and rifles. Something about a rule of lenity
I agree with the plurality that the application of the National Firearms Act (NFA) to Thompson/Center's pistol and conversion kit is sufficiently ambiguous to trigger the rule of lenity, leading to the conclusion that the kit is not covered. --I found other links... one sec