The problem is that the court reaffirmed Miller in both Heller & McDonald. Miller states that weapons MUST have suitability in a militia. Militia weapons in common use at the time. The court refused to overturn Miller as a mistake or as being inconsistent with it's new (or maybe antique) holding of the 2nd Amendment as an individual right to self defense. Militia weapons are NOT essential for self defense. Nor are they essential for hunting (not mentioned in Miller but still part of the right). So in short the court has to either overturn Miller or suffer the unintended consequences of making fully automatic "militia" weapons (& probably more) available for self defense.