Here is Virginia’s laws on this matter for example, which mirror multiple other states laws:
Article 8. Unorganized Militia. § 44-85. Regulations and penalties.
Whenever any part of the unorganized militia is ordered out, it shall be governed by the same rules and regulations and be subject to the same penalties as the National Guard.
1930, p. 965; Michie Code 1942, § 2673(71); 2015, c. 221.
§ 44-86. When ordered out for service.
The commander in chief may at any time, in order to execute the law, suppress riots or insurrections, or repel invasion, or aid in any form of disaster wherein the lives or property of citizens are imperiled or may be imperiled, order out the National Guard and the inactive National Guard or any parts thereof, or the whole or any part of the unorganized militia. When the militia of this Commonwealth, or a part thereof, is called forth under the Constitution and laws of the United States, the Governor shall order out for service the National Guard, or such part thereof as may be necessary; and he may likewise order out such a part of the unorganized militia as he may deem necessary. During the absence of organizations of the National Guard in the service of the United States, their state designations shall not be given to new organizations.
1930, p. 965; Michie Code 1942, § 2673(72); 1958, c. 393.
§ 44-87. Manner of ordering out for service.
The Governor shall, when ordering out the unorganized militia, designate the number to be so called. He may order them out either by calling for volunteers or by draft.
1930, p. 965; Michie Code 1942, § 2673(73); 1944, p. 25; 1958, c. 393; 1984, c. 765.
§ 44-88. Incorporation into the Virginia Defense Force.
Whenever the Governor orders out the unorganized militia or any part thereof, it shall be incorporated into the Virginia Defense Force until relieved from service.
1944, p. 25; Michie Suppl. 1946, § 2673(73); 1984, c. 765; 2011, cc. 572, 586.
§ 44-89. Draft of unorganized militia.
If the unorganized militia is ordered out by draft, the Governor shall designate the persons in each county and city to make the draft, and prescribe rules and regulations for conducting the same.
1930, p. 965; Michie Code 1942, § 2673(74).
§ 44-90. Punishment for failure to appear.
Every member of the militia ordered out for duty, or who shall volunteer or be drafted, who does not appear at the time and place ordered, shall be liable to such punishment as a court-martial may direct.
1930, p. 965; Michie Code 1942, § 2673(75); 1958, c. 393.