In the 1939 case of Danforth v. United States, the Supreme Court ruled that a defendant could not be convicted solely on the basis of his own uncorroborated confession. The case involved an appeal by William Danforth who had been convicted for mail fraud based largely on his own confession to postal inspectors. He argued that there was insufficient evidence apart from this confession to support his conviction and appealed all the way up to the Supreme Court after lower courts upheld his sentence. In its decision, written by Justice Felix Frankfurter, the court agreed with Danforth's argument and overturned his conviction in a 5-4 ruling. This landmark decision established important precedent regarding confessions and their role in criminal convictions.

In the dissenting opinion for Danforth v. United States, Justice McReynolds argued that the majority's decision to uphold a federal law banning false advertising of seeds was an overreach of Congress' power under the Commerce Clause. He contended that while Congress has authority to regulate interstate commerce, it does not have unlimited power to control all activities affecting such commerce. In this case, he believed that false advertising is more appropriately regulated by individual states rather than at a federal level. Furthermore, he expressed concern about potential abuse and expansion of federal powers if such broad interpretations were allowed to stand unchallenged.