^^^^^^^He doesn't have to ban them. He can just reduce staff at the NFA branch or instruct them to impose a moratorium on reviewing new applications. Either would please the gun-control lobby.
And there you go, a classic bureaucratic solution that makes some left leaning constituants very happy yet provides cover from RKBA'ers being able to say 'they didn't ban anything'.
Or they could go the opposite way and issue a regulation there will be a review of every Class III item, and your time to show up at XXXXX location with the item and paperwork is ________.
It's not in the interest of the executive branch or centric and conservative members of congress' to allow an outright ban. But they can make ownership very painful.
But we'll see.