In the case of United States et al. v. New York Telephone Co., 1945, the Supreme Court ruled that telephone companies are required to assist law enforcement agencies in implementing wiretaps. The court held that under Section 605 of the Federal Communications Act, it was not illegal for a telephone company to provide technical assistance to law enforcement officials who were legally authorized to intercept a communication. This ruling came after New York Telephone Company refused federal agents' request for help in installing a pen register device on one of its customer's lines due to privacy concerns and potential liability issues. The decision clarified that while private communications cannot be intercepted without authorization, once such authorization is granted by legal authorities, phone companies have an obligation to cooperate.

In the dissenting opinion for the United States v. New York Telephone Co., it was argued that the majority's decision to allow wiretapping without a warrant violated Fourth Amendment rights against unreasonable searches and seizures. The dissenters believed that this ruling gave law enforcement too much power, potentially leading to abuses of civil liberties. They contended that any evidence obtained through such means should be considered inadmissible in court due to its unconstitutional acquisition. Furthermore, they expressed concern over potential misuse of these powers by government agencies beyond just law enforcement, which could lead to widespread invasions of privacy with little recourse for citizens affected by them.