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State Duty[edit]

When National Guard units are not under federal control, the governor is the commander-in-chief of the units of his or her respective state, territory (Guam, Virgin Islands), or commonwealth (Puerto Rico). The President of the United States commands the District of Columbia National Guard, though this command is routinely delegated to the Commanding General of the DC National Guard.[22] States are free to employ their National Guard forces under state control for state purposes and at state expense as provided in the state's constitution and statutes. In doing so, Governors, as commanders-in-chief, can directly access and utilize the Guard's federally assigned aircraft, vehicles and other equipment so long as the federal government is reimbursed for the use of fungible equipment and supplies such as fuel, food stocks, etc. This is the authority under which Governors activate and deploy National Guard forces in response to natural disasters. It is also the authority under which Governors deploy National Guard forces in response to man-made emergencies such as riots and civil unrest, or terrorist attacks.[23]

The Governor can activate National Guard personnel to 'State Active Duty' in response to natural or man-made disasters or Homeland Defense missions. State Active Duty is based on State statute and policy as well as State funds, Soldiers and Airmen remain under the command and control of the Governor. The federal Posse Comitatus Act (PCA) does not apply.
Title 32 Full-Time National Guard Duty. (Federally funded, but command and control remains with the State Governor through his Adjutant General.)

Title 32 activation can only be done by the President or SECDEF with the approval and consent of the state Governor.

The most common duty for National Guard personnel is Inactive Duty for Training (IDT). This is the traditional weekend a month and two week summer training periods.
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http://en.wikipedia.org/wiki/National_Guard_of_the_United_States


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Federal Duty[edit]

Title 10, service means full-time duty in the active military service of the United States. The term used is federalized. Federalized National Guard forces have been ordered, by the President to active duty either in their reserve component status or by calling them into Federal service in their militia status.[22] There are several forms:

Voluntary Order to Active Duty.
Federalized with the Soldier's or Airman's consent and the consent of their Governor.

Partial Mobilization.
In time of national emergency declared by the President for any unit or any member for not more than 24 consecutive months.

Presidential Reserve Call Up.
When the President determines that it is necessary to augment the active forces for any operational mission for any unit or any member for not more than 270 days.

Federal Aid for State Governments.
Whenever an insurrection occurs in any State against its government, the President may, upon the request of its legislature or of its governor call into Federal service such of the militia of the other States. This is a statutory exception to the PCA

Use of Militia and Armed Forces to Enforce Federal Authority.
Whenever the President considers that unlawful obstructions, assemblages, or rebellion make it impracticable to enforce the laws of the United States in any State or Territory, he may call into Federal service such of the militia of any State. This is another statutory exception to the PCA

Interference with State and Federal law.
The President, by using the militia or the armed forces, or both, or by any other means, shall take such measures as he considers necessary to suppress, in a State, any insurrection, domestic violence, unlawful combination, or conspiracy.

Air and Army National Guard.
Air and Army National Guard can specifically be called into Federal service in case of invasion, rebellion, or inability to execute Federal law with active forces.

In the categories listed above, Army and Air National Guard units or individuals may also be mobilized for non-combat purposes such as the State Partnership Program, humanitarian missions, counterdrug operations, and peacekeeping or peace enforcement missions.[22]
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http://en.wikipedia.org/wiki/National_Guard_of_the_United_States