evidence: To implement a draft, Congress and the president must authorize one. Congress passes legislation that the president then signs. In order to initiate a draft, the government needs to know who is eligible to be called up.[5] This is typically a segment of the population comprised of men between the ages of 18 and 35. The Selective Service System was enacted in its earliest form in 1917 and has been resurrected, modified, and used throughout the 20th century, as needed, to create and maintain a registry of potential draftees in the event the country needs to mobilize for large-scale war.[6]