Correct.
Why was the U.S. Supreme Court interested in "some reasonable relationship to the preservation or efficiency of a well regulated militia"?
"they may have shown that a sawed-off shotgun is indeed a useful militia weapon."
Perhaps they could have. Who were Miller's attorneys going to use to testify in court as to whether or not a weapon was suitable for a state's Militia?
Since this decision affects a state Militia, shouldn't each individual state be the one to decide which weapons their Militia will use? Shouldn't the state be testifying? Aren't these the weapons which the federal government "shall not infringe"?
What if Mr. Miller's weapon didn't qualify as a Militia-type weapon? What would have happened?
They could have used the act's own words, which specifically exempted the military from the regulations about short barreled rifles and shotguns. The military can have all the short barreled shotguns it wants. Law enforcement was also exempt, and police assume a paramilitary role in times of emergency. It was illogical for the court to refuse to see that "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 . . ." when the law was written so that only military and paramilitary organizations could have them.
The state had no standing in this case, since the state was not being sued or prosecuted.
Mr. Miller had standing to present evidence that his shotgun was a militia-type weapon, and was therefore one of the "arms" the individual ownership of which is protected by the Second Amendment, but he didn't show up.