In Estep v. United States (1945), the U.S. Supreme Court ruled in favor of William E. Estep, who had been convicted for refusing to submit to induction into the military service during World War II after his claim for classification as a conscientious objector was denied by his local draft board and on appeal. The court held that when a Selective Service System registrant is criminally prosecuted for not obeying an order to report for induction, he can defend himself by proving that the draft board made a "blatantly lawless" decision in classifying him as available for military service despite substantial evidence supporting his claim of exemption or deferment from such service under applicable provisions of the Selective Training and Service Act of 1940.

In the dissenting opinion for Estep v. United States, Justice Frankfurter argued that the majority's decision undermined the Selective Service System and its ability to function effectively during wartime. He believed that Congress had intended for local draft boards to have final authority in determining a person's eligibility for conscientious objector status, subject only to review by higher administrative bodies within the system itself. According to him, allowing judicial review of these decisions would lead to an unmanageable flood of litigation and disrupt military operations at a critical time. Furthermore, he contended that Estep had failed to exhaust his administrative remedies before seeking relief in court - something required under established principles of administrative law. Finally, he disagreed with the majority's interpretation of "religious training and belief," arguing it was too narrow and excluded individuals who held deeply-held moral or ethical beliefs against war but did not belong to any traditional religious group.