In the case of Nardone et al. v. United States in 1939, the U.S Supreme Court ruled that evidence obtained through wiretapping by federal agents could not be used in court because it violated the Communications Act of 1934. The defendants, Frank Nardone and others, were convicted for violating a law prohibiting alcohol transportation during Prohibition based on evidence gathered from intercepted telephone conversations. They appealed their convictions arguing that this was an illegal use of wiretap information as per Section 605 of the Federal Communications Act which prohibited interception and divulgence of communication signals without authorization. The Supreme Court agreed with them stating that Congress intended to protect private communications when they passed Section 605 and thus any unauthorized interceptions even by government officials would violate this provision unless there was explicit permission granted by Congress itself for such actions. Therefore, any evidence obtained via these means should be excluded from trials as 'fruit from a poisonous tree'. This decision reinforced privacy rights against unwarranted surveillance while also emphasizing Congressional authority over executive agencies' investigative methods.

In the dissenting opinion for Nardone et al. v. United States, Justice Butler argued that the majority's interpretation of Section 605 of the Federal Communications Act was incorrect and overly broad. He contended that this section only prohibits unauthorized persons from intercepting or divulging communications, not government officials conducting investigations in public interest. According to him, Congress did not intend to limit law enforcement's ability to use wiretapping as an investigative tool when they enacted this legislation; rather it aimed at preventing unauthorized interception by private individuals or entities for malicious purposes such as blackmail or industrial espionage. Therefore, he believed that evidence obtained through federal agents' wiretaps should be admissible in court proceedings since these actions were taken under their duty and authority without any personal gain involved.