The two-part mission of the Selective Service System is:
To register men and maintain a system that, when authorized by the President and Congress, rapidly provides personnel in a fair and equitable manner while managing an alternative service program for conscientious objectors.
Selective Service would provide personnel to the military by conducting a draft using a list of young men's names gathered through the Selective Service registration process. Virtually all men - ages 18 through 25 - must register. Only if there is high compliance with this law, will a future draft be fair and equitable. The obligation of a man to register is imposed by the Military Selective Service Act (PDF format here), which establishes and governs the operations of the Selective Service System.
The Alternative Service Program would provide public service work assignments in America's communities in lieu of military service for men classified as conscientious objectors to all military service.