The War Department bars the enlistment of men under eighteen without parental approval
The War Department published revised regulations concerning enlistment of young men to the Union Army. From now on, no-one under the age of eighteen years was to be enlisted or re-enlisted without the "written consent of his parents, guardian, or master." Recruiting officers were enjoined to take particular care in knowing the true age of the recruit presenting himself. Only when the form was completed could the enlistment proceed to an examination. (By John Osborne)
War Department, Thomas M. O'Brien, Oliver Diefendorf (eds), General Orders of the War Department, Embracing the years 1861, 1862, 1863 ... (New York: Derby and Miller, 1864), 196.