In Mulloy v. United States (1969), the Supreme Court ruled in favor of John W. Mulloy, who had been convicted for refusing induction into the armed forces during the Vietnam War era. The court held that his local draft board violated due process by not providing a basis for its decision to deny him conscientious objector status and failing to reopen his classification upon receiving new information supporting his claim. This ruling set an important precedent regarding procedural fairness in Selective Service System proceedings, asserting that when a registrant makes non-frivolous allegations presenting facts not previously considered by their draft board which could potentially qualify them for deferment or exemption, they are entitled to have their classifications reopened and reconsidered.

In the dissenting opinion for Mulloy v. United States, Justice Harlan disagreed with the majority's decision to overturn Mulloy's conviction on grounds of a violation of his Fifth Amendment rights. He argued that there was no evidence suggesting that Mulloy had been tricked or coerced into waiving his right against self-incrimination when he appeared before the draft board without counsel and answered questions about his Communist affiliations. Instead, Justice Harlan believed that it was reasonable for the draft board to assume that Mulloy understood his rights since he had previously invoked them during an FBI interview. Furthermore, Justice Harlan contended that even if there were some ambiguity in this regard, any error made by the trial court did not warrant reversal because it would have been harmless beyond a reasonable doubt given other overwhelming evidence of guilt presented at trial.