In the case of On Lee v. United States, 1951, the Supreme Court ruled that a federal agent's use of an informant to secretly record conversations with the defendant did not violate his Fourth Amendment rights against unreasonable searches and seizures. The court held that since there was no physical intrusion into a constitutionally protected area by law enforcement officials, there was no search or seizure within the meaning of the Fourth Amendment. The decision also noted that Mr. Lee had willingly spoken to an undercover informant without knowing he was speaking to someone working for law enforcement; therefore, he could not claim any constitutional protection for those statements under his Fifth Amendment right against self-incrimination.

In the dissenting opinion for ON LEE v. UNITED STATES, Justice Douglas argued that the majority's decision violated Lee's Fourth Amendment rights against unreasonable searches and seizures. He contended that using an informant to secretly record a conversation in a private setting constituted an invasion of privacy and was equivalent to an unlawful search. Furthermore, he disagreed with the majority’s view that no trespass had occurred since the informant was invited into Lee’s business; instead, he believed this invitation did not extend to secret government surveillance or intrusion by electronic devices. According to Justice Douglas, such actions were contrary to principles of fairness and decency inherent in American law enforcement practices.