In the case of United States v. Ramsey et al., 1976, the U.S Supreme Court ruled that customs officials do not need a warrant to search mail entering the country from abroad. The defendants were charged with conspiracy and possession of stolen treasury bills which had been found in an envelope marked as personal correspondence during a routine check by customs officers at John F Kennedy Airport, New York. They argued that this violated their Fourth Amendment rights against unreasonable searches and seizures. However, the court held that border searches fall under "reasonable" exceptions due to national sovereignty interests and therefore do not require probable cause or a warrant. This decision upheld Congress's power to authorize such inspections without violating constitutional protections.

In the dissenting opinion for United States v. Ramsey et al., Justice Brennan, joined by Justices Stewart and Marshall, argued that the majority's interpretation of the Fourth Amendment was overly broad. They contended that not all border searches should be considered reasonable simply because they occur at a border or its functional equivalent. The dissenting justices believed this blanket approval violated individuals' rights to privacy and protection from unreasonable searches and seizures as guaranteed by the Constitution. Instead, they proposed a more nuanced approach where reasonableness would be determined on a case-by-case basis considering factors such as degree of intrusion into personal privacy and government interests in preventing illegal entry.