The lawyer defending that guy in that late '30s case was an ignorant idiot. Had he done any research at all he would have found that shotguns had been used in trench warfare in WWI. even shortened ones.
If the present court made a ruling based upon that case, it would overturn the 1994 gun ban because some of that list were military styled arms.
That lawyer did not make an appearance at the Supreme Court. He didn't need to produce such evidence or results of research, the trial judge knew all that, and threw the case out before trial. The government appealed directly (not via the Court of Apeals, which is highly unusual) to the Supreme Court, and presented the only arguments heard or briefed, there.
If you'll take a link to the "Here" link in post 244, you'll see that the government tried to make the "states rights" case, but the court wasn't having that, and did not even mention most of the governments arguments in it's very narrow decision.