In Rathbun v. United States, the Supreme Court ruled that it was not a violation of federal wiretap laws for one party in a phone conversation to record the call without informing the other party. The case arose when Mr. Rathbun and his wife were charged with illegal gambling operations based on evidence obtained from a recorded telephone conversation between Mrs. Rathbun and an unidentified individual, which was recorded by Mr. Rathbun himself without notifying his wife or the third person involved in their discussion about betting information. The court held that since Congress intended to protect communication privacy from unauthorized interception by third parties rather than participants themselves, such recording is permissible under law as long as one participant consents even if others are unaware of this action.

In the dissenting opinion for Rathbun v. United States, Justice Frankfurter disagreed with the majority's interpretation of Section 605 of the Federal Communications Act. He argued that this section was intended to protect private conversations from being intercepted and used as evidence in court without consent from all parties involved. The majority held that if one party consents to a conversation being overheard or recorded, then it is not illegal under Section 605; however, Frankfurter believed this view undermined privacy rights and contradicted Congress' intent when drafting the law. Furthermore, he pointed out inconsistencies in previous rulings regarding similar cases which further complicated its interpretation. Ultimately, he felt that only through legislative action could clarity be brought to these issues rather than through judicial reinterpretation.