This is some research I did regarding the talking point coming from my Republican family that the President does not have legal authority to deploy troops until requested by the states.
http://www4.law.cornell.edu/uscode/html/uscode10/usc_sec_10_00012304----000-.html
TITLE 10 > Subtitle E > PART II > CHAPTER 1209 > § 12304
§ 12304. Selected Reserve and certain Individual Ready Reserve members; order to active duty other than during war or national emergency
Release date: 2004-03-18
(a) Authority.-- Notwithstanding the provisions of section 12302 (a) or any other provision of law, when the President determines that it is necessary to augment the active forces for any operational mission or that it is necessary to provide assistance referred to in subsection (b), he may authorize the Secretary of Defense and the Secretary of Homeland Security with respect to the Coast Guard when it is not operating as a service in the Navy, without the consent of the members concerned, to order any unit, and any member not assigned to a unit organized to serve as a unit of the Selected Reserve (as defined in section 10143 (a) of this title), or any member in the Individual Ready Reserve mobilization category and designated as essential under regulations prescribed by the Secretary concerned, under their respective jurisdictions, to active duty (other than for training) for not more than 270 days.
(b) Support for Responses to Certain Emergencies.-- The authority under subsection (a) includes authority to order a unit or member to active duty to provide assistance in responding to an emergency involving--
(1) a use or threatened use of a weapon of mass destruction; or
(2) a terrorist attack or threatened terrorist attack in the United States that results, or could result, in catastrophic loss of life or property.
(c) Limitations.--
(1) No unit or member of a reserve component may be ordered to active duty under this section to perform any of the functions authorized by chapter 15 or section 12406 of this title or,
except as provided in subsection (b), to provide assistance to either the Federal Government or a State in time of a serious natural or manmade disaster, accident, or catastrophe.
How does the phrase go...LIERS.