Historically speaking, it gets real dicey. The historical precedent of this part of the constituion raises the question of which is superior, a state militia, or national army?
In 1786/1794, state militias rebelled against national goverment policy. In the latter they were put down by a nationl army.
Section two of the Constitution gives the president power, or commanding power of a national army, which is never mentioned in the Constituton--state militias are legitimate "when called into national service"--which is ultimately dicey, since the legislature is the official body of gov't which declares war.