Article 1, Section 8, Clause 16: Regulation of the Militia

To provide for organizing, arming, and disciplining, the Militia, and for governing such Part of them as may be employed in the Service of the United States, reserving to the States respectively, the Appointment of the Officers, and the Authority of training the Militia according to the discipline prescribed by Congress;

This clause makes plain that the militia, in time of peace, is under state control. However, Congress is empowered to make appropriations to organize, arm, and train the militia, and to make regulations for their government once the militia are federalized. However, the states have exclusive authority to appoint officers in their militias, and control their training. Congress may, however, enact statutes mandating a particular syllabus for the training of the militia, which the states must adhere to.

During the Second World War, the officers of the Regular Army had a generally low opinion of National Guard officers, with rare exceptions. One was Robert S. Beightler, commander of the 37th Infantry Division, who rose to the rank of major general. His division was originally an Ohio National Guard division, and Beightler himself was a political appointee (he was a personal friend of the Ohio governor.) However, he had served as an officer in the Army of the United States during the First World War, though never a regular officer.