Ignorance isn't a defense. So this is not the first reversal on a gun that has been sold. See my thread in general "brace ban". The last couple basically the manufacturer provided sale docs to the atf, then the wholesalers provided next sale, then local gun shops provided 4473s. The honeybadger is more popular than the previous two, but the agency is well practiced at this point.
To the feds this is no different than having your pappys grenade from Grenada. You had no idea it was real but you will still catch the charges
What about forced ignorance? If the "law" isnt published and readily referenced, how can it be enforced? Isnt that like a speed limit sign with a white background and white numbers? How fast can you go since you cant see the numbers? (assuming they are not relief printed)