Comment Re:Military Police? (Score 3, Informative) 203
No, it's within the limits of the law. The National Guard Military Police units are considered to be troops controlled by the individual state (think the 13 colonies initially). In this case they were ordered onto the street by the state governor.
As for Federal troops, the Posse Comitatus Act deals with using Federal troops in police enforcement and has only been around since 1878. There has been an ongoing tension between what powers belonged to the states and what belonged to the federal government.
Now, in reality, there's relatively little difference between the Guard and federal troops, and the Guard can be "federalized" with an order from the President, and there are several other exceptions to the Posse Comitatus Act. But, it falls within the letter of the law.