There have been two challenges to assault weapons bans thus far I believe, one in California and the other in Washington, D.C. In the California one, the Court upheld the ban and mentioned about how the ban does not infringe on hunters and sport shooters, which showed that they had a total lack of understanding of the Second Amendment. In the Washington, D.C. upholding, the Court agreed that so-called "assault weapons" are very much weapons in common usage, but they determined, based on a study conducted by the Brady Campaign, that semiautomatic weapons are so dangerous that they can still be outlawed. This is odd, considering the vast majority of all handguns are either semiautomatic or functionally identical.
I wonder how the press would have reacted if they had shot down the law based on going by a study that had been conducted by a gun rights group. We'd have never heard the end of it.
Even D.C. v Heller was 9-0 on whether the Second Amendment was written to protect an individual right to keep and bear arms. The 5-4 split was that the four dissenting justices said that while it was originally written to protect an individual right, that was the 18th century and what applied as a right in the 18th century has no place in the 21st century.