>all able-bodied male citizens of the United States and all other able-bodied males who have . . . declared their intention to become citizens of the United States,” between the ages of eighteen and forty-five.
32 U.S. Code § 313 - Appointments and enlistments: age limitations
(a)To be eligible for original enlistment in the National Guard, a person must be at least 17 years of age and under 45, or under 64 years of age and a former member of the Regular Army, Regular Navy, Regular Air Force, or Regular Marine Corps. To be eligible for reenlistment, a person must be under 64 years of age.
(b)To be eligible for appointment as an officer of the National Guard, a person must—
(1)be a citizen of the United States; and
(2)be at least 18 years of age and under 64.