Sorry, but this is the justification for the ruling, not its basis. The outcome was determined first then they had to find a way to justify it. Or as the Queen of Hearts said, "Sentence first - verdict afterwards." Do not think that this can be used as a precedent for an outcome that the court does not favor.
The court has already upheld the individual right to firearm ownership in Heller.
But perhaps they just had a random moment of clarity.
Like I said, I am not up on this at all. But, I know people here are and will be. Maybe together, we come up with a response that will stop this madness.