Notice they didn't note that the right to keep and bear arms is mandated by the 2nd Amendment, but rather that is was merely a traditional concept? That's because they are ruling under administrative law, which is presumed to be applied to all the natural persons in order to make them corporate employees of the federal government. That's how "rights" gets turned into "privileges," and why the 14th Amendment becomes relevent - it addresses federally-created corporate persons and employees.
Don't like it? Tough - the status change is a judicially recognized presumption. And therefore, because it is not proven fact, it need not be disproven. And so there are no judicially recognized methods to dismiss this presumption, let alone disprove it.
Oh, and they've also ruled that they don't have to inform you of this presumption, either, and if you even step foot in court you've accepted their presumption by showing up (and of course they throw you in jail if you don't).
BTW, this is also the little gotcha that defeats people who claim their rights against unfair taxation.
Kafka was a piker.
The logical gymnastics the Court had to go through are a result of some really bad decisions regarding the 14th amendment's privileges and immunities clause, which basically say, with no historical support, that the P&I guaranteed are those due strictly to being a citizen of the US, rather than "immunities" against infringements of preexisting rights.
My favorite quote:
[W]hereas the Supreme Court has previously incorporated rights the colonists fought for, we have here both a right they fought for and the right that allowed them to fight.
Amen.