Judge Robert King is flat out making things up.
During the oral arguments, he brought up the same argument, and it was explained to him at length that there are fundamental differences in functionality between an AR-15 and an M16, namely that the latter is capable of automatic fire and the former is not. That capability, and by extension the existing federal laws which restrict (not outright ban just restrict) automatic weapons, is what Scalia was using as an example of permissible restrictions.
This is compounded by the handwaving away of the “in common use for lawful purpose” part of the Heller decision. The AR-15 is the single most common model of rifle in the country. If that doesn’t meet the threshold of “common use”, I have no idea what does.
These deliberate misreadings of Heller are especially galling considering that Scalia joined in dissents against decisions not to hear those previous AWB cases, stating that such laws directly controverted the decision which he authored. It’s awfully disingenuous to claim Heller means something when its author has said otherwise.
And even beyond Heller, the Miller decision controverts King’s opinion as well. “…we have no power to extend Second Amendment protection to the weapons of war that the Heller decision explicitly excluded from such coverage.” Ignoring that Heller did no such thing, Miller stated “In the absence of any evidence tending to show that possession or use of a ‘shotgun having a barrel of less than eighteen inches in length’ at this time has some reasonable relationship to the preservation or efficiency of a well regulated militia, we cannot say that the Second Amendment guarantees the right to keep and bear such an instrument. Certainly it is not within judicial notice that this weapon is any part of the ordinary military equipment, or that its use could contribute to the common defense.”
You have Miller stating that weapons which are not useful in a martial context aren’t protected, and now King is claiming that weapons which are useful in martial context are not protected. So which is it? It can’t be both, and King is outranked here. It also doesn’t make any Constitutional sense. If the 2nd Amendment is intended to allow people to participate in a militia, I’m not sure how he would propose the people accomplish that if they can be prohibited from owning the weapons necessary to participate.
Between Miller and Heller, you have essentially a two part test for whether a particular type of weapon is protected. Could it be useful in a martial context? Is it in common use for lawful purpose? The answer to both of those questions must be no.