It's a fact, supported by case law.
As for case law: I don't recall where anyone has claimed that the States (or the Feds, for that matter) have been restrained by case law on Second Amendment grounds. I can't think of any examples. Can you point me to a post where someone has made such a claim?
As for it being a fact, which you distinguished from case law: Justice Clarence Thomas has some things to say about that:
THE SECOND AMENDMENT: A GUARD FOR OUR FUTURE SECURITY by Andrew M. Wayment
In his concurring opinion in Printz v. United States, Justice Thomas acknowledged this fact: "Marshaling an impressive array of historical evidence, a growing body of scholarly commentary indicates that the 'right to keep and bear arms' is, as the Amendment's text suggests, a personal right."[160]
Furthermore, Justice Thomas speculated that "[i]f . . . the Second Amendment is read to confer a personal right to 'keep and bear arms,' a colorable argument exists that the Federal Government's regulatory scheme, at least as it pertains to the purely intrastate sale or possession of firearms, runs afoul of that Amendment's protections."[161]
Towards the end of his opinion, Justice Thomas made an interesting prediction: "[P]erhaps, at some future date, this Court will have the opportunity to determine whether Justice Story was correct when he wrote that the right to keep and bear arms 'has justly been considered, as the palladium of the liberties of a republic."' [end of excerpt]
-- THE SECOND AMENDMENT: A GUARD FOR OUR FUTURE SECURITY
IMO, you should listen to what Justice Clarence Thomas says.
"As for case law: I don't recall where anyone has claimed that the States (or the Feds, for that matter) have been restrained by case law on Second Amendment grounds."
I didn't say anyone claimed that. I said that no defendant has ever successfully used the second amendment as protection from some state law. If the second amendment protects a citizen from state gun laws, then where are the cases demonstrating that?
I can cite a half-dozen where the courts have ruled just the opposite -- that the second amendment affords no protection from state laws.