In the case of United States v. Donovan et al., 1976, the U.S. Supreme Court ruled that wiretap evidence obtained by foreign law enforcement agencies could be used in American courts even if it was collected without a warrant or probable cause, as long as it did not violate any treaty obligations between the two countries involved and was not conducted with intent to evade constitutional requirements. The defendants were charged with conspiracy to import narcotics into the U.S from Mexico based on wiretapped conversations recorded by Mexican authorities without warrants or judicial supervision. They argued that this violated their Fourth Amendment rights against unreasonable searches and seizures but the court disagreed stating that such protections do not apply outside U.S territory unless there is deliberate evasion of constitutional requirements.

In the dissenting opinion for United States v. Donovan et al., Justice Brennan, joined by Justices Stewart and Marshall, argued that the majority's decision to allow warrantless wiretapping in domestic security cases was a violation of Fourth Amendment rights. They contended that there is no constitutional basis for distinguishing between foreign threats and domestic ones when it comes to surveillance without a warrant. The dissenters also expressed concern about potential abuses of power if such surveillance were left unchecked, noting historical instances where similar powers had been misused against political dissidents or minority groups. Furthermore, they disagreed with the majority's assertion that national security concerns outweighed individual privacy rights in this context; instead arguing that robust protections for civil liberties are essential even - perhaps especially - during times of perceived threat to national security.