Militia Act of 1903

The Militia Act of 1903 (32 Stat. 775), also known as "The Efficiency in Militia Act of 1903", also known as the Dick Act, was legislation enacted by the United States Congress which codified the circumstances under which the National Guard could be federalized. It also provided federal funds to the National Guard to pay for equipment and training, including annual summer encampments. In return, the National Guard began to organize its units along the same lines as the regular Army, and took steps to meet the same training, education and readiness requirements as active duty units.

During the nineteenth century, the militia in each U.S. state and territory operated under the Militia Acts of 1792. Under these laws, the question of state versus federal control of the militia was unresolved. As a result, the federal government could not rely on the militia for national defense. As an example, during the War of 1812, members of the New York Militia refused to take part in operations against the British in Canada, arguing that their only responsibility was to defend their home state. In another instance, Martin Chittenden, the Governor of Vermont, unsuccessfully attempted to recall his state's militia from the defense of Plattsburgh, claiming that it was illegal for them to operate outside Vermont's borders.

Because the issue of state versus federal control was not resolved, the federal government resorted to the creation of "volunteer" units when it needed to expand the size of the Army. These units of United States Volunteers were not militia, though often they consisted of militia units which had volunteered en masse, nor were they part of the regular Army. This solution was employed during the Mexican–American War, and in the Union Army during the American Civil War.

...
Wikipedia