I addressed this once before in (I think) the M16 forum. The problem with Rock Island in the C.D. of Illinois and with Daulton in the 10th is that they are somewhat old cases and the reasoning applied therein has been soundly rejected by all other circuits. Rock Island has actually been overruled by US v. Ross in the 7th circuit. Daulton raises the same issue in the 10th circuit, and as far as I know Daulton still stands in the 10th, but only because the 10th Circuit hasn't had an opportunity to revisit the issue since 1992. Basicly, I think when Daulton was originally brought, the judges simply weren't as sharp as those in other circuits. If you read the dicta, its fairly clear that they didn't want to invalidate the NFA, but they couldn't find a way to reconcile the NFA with 922(o). All other circuits that have addressed the issue have found that the 922(o) didn't repeal the NFA as was found in Daulton and RIA, but that 922(o) works together with the NFA. That is, since an individual can't register and pay the making tax on a machinegun made after May 1986, the only way to avoid prosecution is to not possess or deal in machineguns made after 1986.