According to this reasoning: "According to the majority’s reasoning, if Congress
and the States lift restrictions on the possession and use of
machineguns, and people buy machineguns to protect
their homes, the Court will have to reverse course and find
that the Second Amendment does, in fact, protect the
individual self-defense-related right to possess a machinegun.
On the majority’s reasoning, if tomorrow someone
invents a particularly useful, highly dangerous selfdefense
weapon, Congress and the States had better ban it
immediately, for once it becomes popular Congress will no
longer possess the constitutional authority to do so. In
essence, the majority determines what regulations are
permissible by looking to see what existing regulations
permit."
It was unlawful to ban MGs in the first place, as they were in common use (though regulated) for self defense of one's home. Oh, I really hope to see a 922o case in the near future