The Constitution – Article I, section 8, clauses 15-16

Militia Clause

“The Congress shall have Power…To provide for calling forth the Militia to execute the Laws of the Union, suppress insurrections and repel Invasions…”

Militia Organization

“The Congress shall have Power…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…”