"The Congress shall have Power * * * To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions."
https://law.justia.com/constitution/us/article-1/58-the-militia-clauses.html
"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"
https://publi-us.org/1787/06/12/article-1-section-8-clause-16-regulation-of-the-militia/
"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...."
https://www.heritage.org/constitution/#!/articles/1/essays/56/organizing-the-militia