The base Polymer 80 frame, which is normally the serialized component, was approved by the ATF. The rest of the components sold in the “Buy Build Shoot Kits”, don’t require a background check. I don’t understand how selling the components together would be considered a violation.
FTA: The ATF previously gave Polymer80 permission to sell unfinished receivers. But the Buy Build Shoot Kits, which are advertised as having “all the necessary components to build a complete...pistol” weren’t submitted to the agency for approval, according to the application for the search warrant. These kits can be “assembled into fully functional firearms in a matter of minutes,” the warrant application says.
Somebody felt that selling a kit that allowed the customer to construct a fully-functioning gun violated the laws prohibiting gun sales without a background check.
"Somebody felt that selling a kit that allowed the customer to construct a fully-functioning gun violated the laws prohibiting gun sales without a background check."
I'd love to see the statutes that person used to come to that conclusion (ie the probable cause).
It normally applies to NFA material, but my bet is this tips in to constructive possession territory. In short its the control of the materials required to create or assemble a firearm or other regulated component. Typical examples would be possessing a < 16” barrel, a collapsible stock, and an appropriate receiver. They dont need to demonstrate that you did assemble an SBR without a tax stamp, merely that you could assemble them to an SBR. Similarly here theyre not selling just an unfinished receiver. Its all of the components necessary to assemble (not manufacture) a regulated firearm.
Edit: see also sibling comments are pistol braces, or “baffles” on the sig MPX. The ATF has never been know for consistency even in cases where they issue a letter.
"...merely that you could assemble them to an SBR"
That's only half true for constructive intent. They also have to prove that there was no lawful configuration for those items. For example, you can own a short barreled upper with a pistol-compliant lower and also own a complete rifle. You have the same parts that could build an SBR, but they have a lawful configuration so you aren't in violation unless you actually put them together in that way.
This theory doesn't generally apply to 80% stock because the finished product is lawful (non-prohibited people can build their own guns). Also, the frame/reciever is the "firearm" regardless of the other parts, so it doesn't matter if they are selling it alone or with additional parts.
For example, if a felon is in possession of just a finished frame, they would go to prison just the same as if it were a completed gun. This could also be a scenario where constructive intent could come into play - where the finished product would not be lawful to own for the felon (that's the case for the frame without the parts too). So there's really no legal difference between selling just the frame kit or the full parts kit.
The big issue in my view is that it seems like quite a few of the ATF's actions over the years don't seem to conform to rule of law, or at least not consistently. For example, I don't know what statute they could be citing to support their current action and of course the back and forth over pistol braces.
The behavior of the ATF seems reminiscent of the Russians prodding US air defense systems by flying bombers right on the periphery. They want to see what they can get away with and what causes too much hubbub. Like you mentioned, their latest action with pistol braces seems to follow this questionable line of unlawful infringement and overreach.
