They've always had it (state sovereignty) and, once again, they are using it. Funny how state sovereignty surfaces; just let the Feds do or fail to do something of great importance to the states, whether it's included in the enumerated or presumed federal powers or not, and the states will very likely fill the vacuum - without conflict, other than possible legal conflict. As I read the news, I sense this is happening right now in immigration, welfare, federal usurpation of educational prerogatives, use of state militia (national guard), possibly in health care, etc. In short, when the feds fail, or in the worst case, simply seize up with a severe case of democratic rigomortis as is happening now (for reasons outside the scope of what's appropriate on this board), we always have the states to keep things running - at least on a domestic basis.