U.S. Law - Using the Military for a Police Function

If there's a state of emergency declared, sure it's legal.

That's what happens every time when the National Guard gets called in, is that what you had in mind?

Actually, that response is less than accurate. Article One, Section Eight deals with the power of the Congress. One paragraph of that section reads:

(Congress shall have the Power) To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions;

The Dick Act of 1905, which created the National Guard, holds that the National Guard is the organized militia of the United States, and that all other citizens exercising their second amendment rights constitute the unorganized militia. To that extent, it is considered legal to call out the militia--i.e., the National Guard--for some types of police fuction. However, i don't know that that authority has ever had a court challenge, and the paragraph of Article One, Section Eight refers to the powers of Congress, not of the governors of the several states.

That says nothing about the regular military of the United States.

Setanta-
Thank you.

I remember now, the Posse Comitatus Act of 1878; translated “the power or force of the country; prohibited using the army to execute the laws of the US; formerly the army had been used as part of federal marshalls posses. The Act remains on the books to express the fundamental division between military & civilian realms; The armed forces are not a law enforcement agency. Congress has authorized the use of the armed forces in some cases, e.g. Little Rock desegregation & Nixon a riot in Detroit;was enacted as part of the dismantling of Reconstruction.