I am guessing that the first person to be brought before a judge will all of them that where sold a grandfather clause.
Not sure what you mean here Travis, but if you think a judge can grandfather those units and thus remove them from the purview of the NFA once the Tech Branch issued that ruling, you are sorely mistaken.
FWIW, Newerguy is correct here. BATFE can, does, and has in the past tracked down parts kits and other contraband items from importers/manufacturers/dealers right to the individual buyer's home address. Witness the improperly demilled Uzi kits imported by Cole, Chinese PPsh41 kits rerouted through other countries, the ill-fated SOCOM M249 and RPD uppers, etc. When BATFE wants customer lists and that sort of info from a dealer, manufacturer or importer to track down what they have determined to be a contraband item, most are cooperative. Not because they necessarily want to, but they know BATFE can make their lives (and their business) very difficult if they don't help. They are, afterall, in the unenviable position of having been caught putting contraband items into the stream of commerce. Don't believe me? Just ask Ernie Wrenn re the SOCOM uppers. Wrenn didn't do himself or his customers any favors by not seeking an advisory opinion on the uppers, and he helped to try and get some of the sold units back, but if you think BATFE can't, or won't, play rough and bend the rules when it fits their need, especially when it relates to NFA weapons, you are mistaken.
Once they have something like a customer list from the dealer/manufacturer/importer, it would be a relatively easy matter to start an investigation and get a search warrant for an individual customer.
As regards the substance of the ruling itself, I hate to say it but I agree with VUPDBlue that the ruling is correct in light of the existing law. That said, I think it could be an easy matter to get around this ruling with a similar device. The trigger on the akins recoils rearward (with the action) backwards into the stock, and is thus temporarily shielded from the users finger until the trigger resets and begins moving forward again. If the shooter pulls the trigger and holds it there without moving their trigger finger, the gun does in fact continue to shoot until empty. I think this may be able to be overcome by simply cutting the stock around the trigger back a bit, so the trigger is never completely shielded from the user's trigger finger. If the trigger was then pulled all the way to the rear, the gun would then fire one round and then the shooter would have to release the trigger to allow it to reset before firing again. If the shooter found the "sweet spot" in the trigger pull - not pulling all the way back, but just enough to fire the gun - and held their trigger finger in exactly the same place, the gun would still work exactly as the unmodified Akins does.