In the case of Cooper v. United States in 1929, the Supreme Court ruled that a search warrant could be issued based on evidence obtained through wiretapping. The defendant, Roy Olmstead, was convicted for conspiracy to violate Prohibition laws and his conviction was upheld by the Supreme Court despite his argument that evidence used against him had been gathered illegally via wiretap. This ruling established an important precedent regarding Fourth Amendment rights and privacy issues related to telephone communications. However, it was later overturned by Katz v. United States in 1967 which held that wiretapping constitutes a "search" under the Fourth Amendment and therefore requires a warrant.

In the dissenting opinion for Cooper v. United States, Justice Butler argued that the majority's decision to uphold a conviction based on evidence obtained through wiretapping was unconstitutional. He believed that this violated the Fourth Amendment rights of citizens against unreasonable searches and seizures. According to him, private telephone conversations should be considered as part of one's personal effects and thus protected by constitutional law from unwarranted intrusion by government authorities. Furthermore, he contended that allowing such practices would set a dangerous precedent where privacy is compromised in favor of state interests or convenience in criminal investigations.