Doesn't have to meddle? Isn't allowed to meddle would be more correct. The 14th Amendment is an odd duck in that it departs from the pattern in the Bill of Rights restricting the Federal government only. The "privileges or immunities" of citizens are now protected from State violation; there is good evidence to suggest that Congress had the right to bear arms specifically in mind.
However, does he have to stop States from committing violations? He can't write a law against it: he's not Congress. Even then, Congress can't pass bills commanding the States to do anything. He can't have the Justice Department sue: they aren't a party that has been wronged.
"Let each state pass a concealed weapon bill." That's about as far as he, as President, can Constitutionally go. It's a stretch to claim that Cain is against 2nd Amendment rights simply because he is mindful of the constraints of federalism.
You're right here. I stand corrected.
I think Attorney General at the direction of the POTUS could have the Justice Dept file a brief to the USSC to ask them to intervene in the event of a state level breach of the US Constitution. I'm reaching back here 25 years to my own time in law school, so bear with me if I mess it up, but perhaps a writ of mandamus? Compelling the state to follow the US Constitution? Not certain here, but pretty certain there are such mechanisms in place. Sorry for calling you and the wife fools. I don't react well to ad hominem attacks....