All male citizens and all male residents of the state who have declared their intention to become citizens of the United States, between the ages of eighteen and forty-five years, not exempt by law, shall be subject to military duty and designated as the militia. All female citizens and all female residents of the state who have declared their intention to become citizens of the United States, between the ages of eighteen and forty-five years, may enlist voluntarily in any women’s unit of the armed forces of the state.