During peacetime each state National Guard answers to leadership in the 50 states, three territories and the District of Columbia. During national emergencies, however, the President reserves the right to mobilize the National Guard, putting them in federal duty status.
While federalized, the units answer to the Combatant Commander of the theatre in which they are operating and, ultimately, to the President.
Even when not federalized, the Army National Guard has a federal obligation (or mission.) That mission is to maintain properly trained and equipped units, available for prompt mobilization for war, national emergency, or as otherwise needed.
The Army National Guard is a partner with the Active Army and the Army Reserves in fulfilling the country's military needs.