It's entirely possible that the USSC could rule that the federal government does not have the authority to impose a mandate that everyone must purchase health insurance, and therefore Obamacare is unconstitutional. This would not automatically mean that states cannot impose such a mandate.
I thought that was obvious.
I'm not sure whether a state could enforce a mandate using a tax/penalty scheme like this if the Feds can't. If it is, in fact, a commerce clause issue and one over which the Feds have regulatory power but it's just the method of enforcement that cannot be used, it will depend on the grounds and whether those grounds are applicable to the States.
I think it will be found constitutional, for a few reasons not the least of which is the blatant use of Scalia's argument from the
Gonzales concurrence in the District Court opinion. That might end up being too rich a plum to pass up.
IOW, nobody knows the answer yet. Is it theoretically possible that the Feds cannot do this but the States can? Probably not, but not for the same reason. Now if that doesn't make sense, nothing will.