As usual to follow up: The restrictions in Heller were put forth without any justification. Let’s just take the felon ban (one that I might be persuaded to agree with).
What other basic rights do we take away from felons once they have served and completed their sentence? They have the right of free speech, petition, free religion. They cannot be forced to quarter soldiers, nor are their homes entitled to less privacy than mine or yours. If they are again charged with a crime, they are entitled to the Fifth and Sixth Amendment protections, along with the civil jury trial provisions of the Seventh. They cannot be subject to cruel and unusual punishments or excessive fines even while serving a sentence.
So why is the Second, exclusive of all others denied to a convicted felon? Do they forfeit the basic right of self-defense? Does their life no longer matter?
An argument could be made that such a thing is a reasonable regulation to deny a firearm to a person who has shown a prior propensity for misusing a firearm, but to a felony tax evader? And how does that mesh with other rights? If someone is convicted of making threats, we don’t restrict their future lawful speech. Why an exception here? The opinion engages in none of that necessary analysis.
And why is banning guns in government buildings okay? If the assumption here is that a person might take a gun into a government building to shoot an official, then why cannot a state make the same assumption that carrying a gun in the home might be used to shoot a domestic partner? Or a gun carried in a private office be used to shoot the boss? The opinion allows the presumption that a gun in certain places will be used for violence, yet it protects the very right itself without any analysis that a people would largely carry guns in government buildings for the same reason they would carry in the home: self-defense, which Scalia holds as fundamental. Yet it ceases in a government building or a school?
If I am at a PTA meeting, the police cannot just roughhouse me and search me without cause, nor can I be banned from the school for criticizing the administration. If I am arrested for a crime on school property, I am still entitled to due process and a jury trial. Yet my fundamental right of self-defense is still present. A person could attack me in a school just as easily as at home or on the street. So why is only my Second Amendment right restricted? The opinion makes no attempt at all to speak to that or to justify those bald assertions of dicta.
Ultimately, it is not my intention to start Gun Control Wars XXXIV in this thread. There may be very well reasoned principles why the right of self defense or the right to keep and bear arms can be restricted in these or other ways, but the reasoning of Heller doesn’t address it or really provide any meaningful limitations on it.
So back to your OP, I can see where a squicky guy like Roberts can read Heller and say, “Shit, due to this reasoning, I can’t have a constitutional justification for outlawing the carrying of machine guns in school!” And, because of the weakness of Heller, he can’t. If Scalia had written a better opinion, lower courts wouldn’t have totally ignored Heller, nor would a cert petition be thought of as a descent into madness.