I suppose you don't understand the 10th Amendment either.  

Amendment X
The powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people.

Surely you can see that state's rights are only relevant when not already controlled by the Constitution.

Despite gun grabbers' best attempt at changing the meaning of the words well regulated (never meant controlled, merely functioning correctly - like a well regulated clock), and their denial that the militia is "the people", I don't think there is any legitimate argument to be made against the Constitution protecting the citizen's right to keep and bear arms.  Therefore state's rights have no relevance whatsoever.  So while you are right, you can't have it both ways, in this instance that is simply not the case.