No, I never argued that the Miller decision found it unconstitutional. My interpretation of the U.S. Supreme Court decision in Miller is that IF it is shown that a weapon covered by the NFA was useful to a Militia, then the tax on that particular weapon would be unconstitutional.
In my opinion, the case would have to be presented by a state or a state's Militia, saying that the tax on that particular weapon infringes on the ability of that particular state to form a state Militia (it's possible that not all states use identical weaponry).
This is probably why the NFA is still being enforced.
Miller and Layton were charged with a felony. The prosecution sought from the Supreme Court a reversal so that Miller and Layton could be tried. If your understanding of Miller is correct, then why did the Supreme Court not tell the lower court to convict if the defendants are not a militia?
Why don't you descibe what actions you think the lower court was obligated to take, given the meaning you ascribe to the Miller decision?
Try to remember that the description you give must outline what evidence can be used to convict Miller or Layton at trial. That was the basis of the appeal from the prosecution. The District Court judge, in his original dismissal felt fully justified by application of the Second Amendment. What modification to that understanding did the Supreme Court mandate be applied to the trial of Miller and Layton? What circumstances would result in an acquittal of Miller and Layton? From a precedential standpoint, what evidence would result in an acquittal of anybody else charged with violating NFA 34?
Assume today, that an otherwise law-abiding citizen is charged under NFA 34 for possessing an M16 without a tax stamp. What would be required for conviction under your understanding of the Miller decision?
This statement of yours is very revealing.
When you write "the case would have to be presented" you completely ignore the reason why the Miller decision was made. It was made to satisfy a prosecutor who challenged a dismissal. The prosecution wanted a reversal so that a trial of Miller and Layton could take place.
The only legal interest that permitted the prosecution to come to the Supreme Court was in having the District Court judge reversed with guidance that would permit the trial of Miller and Layton. The trial of Miller and Layton is the only thing which we can know with certainty was the object of the Miller decision. Applicability to other cases requires comparing the circumstances of Miller or Layton to other possible defendants. The prosecution, in fact, would have lacked "standing" to apply for anything else.
For all we know, a later Supreme Court might rule that militias lack standing because the text of the Second Amendment protects "the right of the people to keep and bear arms", and NOT "the right of the militias to keep and bear arms". I know of no "collective rights" whatever. Even corporations are treated in court as "fictitious persons" and not as collectives.