When any part of the Wisconsin National Guard is called into service of the United States, the adjutant general (who is appointed by the governor) may recruit volunteers to the WSDF to serve within the borders of Wisconsin.

Initially, the War Department only requested one volunteer regiment from Wisconsin, leaving thousands of men eager to serve militarily but unable to enter the war until much later as the conflict continued longer than the federal government had anticipated.

The desire of these men to serve, along with a fear of domestic unrest caused by Confederate sympathizers, caused the Wisconsin Legislature and Governor Louis P. Harvey to create a legal framework for local militia companies to organize, drill, and serve as a home guard unit capable of handling state emergencies.

[1] Therefore, the WSDF can be reactivated either by an act of legislature or by an executive order by the Governor of Wisconsin.

Under Wisconsin law, members of the state defense force who are activated during an emergency are guaranteed a leave of absence from their place of employment, and must be reinstated to their former position when their deployment ends, without loss of pay, seniority, health insurance coverage, or other benefits.