Miss. Code Ann. § 33-5-11

The Governor, when ordering out the unorganized militia, shall designate the number and classes to be called. He may order them out either by calling for volunteers or by draft. He may attach them to the several organizations of the National Guard or the Mississippi State Guard, as may be best for the service, provided that no additional organization or unit shall be created from the unorganized militia until the units of the National Guard are brought to their full authorized strength. 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.