I suspect ATF. Vertical grips are considered a no-no, makes it a short barreled rifle, in fact the picture with the pistol grip could also be considered a short barreled rifle. That is why the short shotguns have "birds head" type grips instead of pistol grips. Since they change their minds sometimes daily unless you have a tax stamp for a short barreled rifle to be safe, you never can be too safe with federal regulators. I wonder if they were the reason for it's demise or if the T/C had a stronger base it couldn't overcome?