Marshall v. United States was a Supreme Court case decided in 1972. The case involved a challenge to the constitutionality of the federal government's power to prosecute a defendant for a crime that was committed on an Indian reservation. The defendant, Marshall, was charged with the illegal possession of firearms on the Yakima Indian Reservation in Washington State. Marshall argued that the federal government did not have the authority to prosecute him for a crime committed on the reservation, as the reservation was a sovereign nation and the federal government had no jurisdiction over it. The Supreme Court ruled in favor of the federal government, holding that the federal government did have the authority to prosecute Marshall for the crime committed on the reservation. The Court reasoned that the federal government had the power to regulate activities on Indian reservations, and that this power extended to criminal prosecutions. The Court also noted that the federal government had a special trust relationship with Indian tribes, and that this trust relationship gave the federal government the authority to protect the tribes from criminal activity. The decision in Marshall v. United States was significant in that it established the federal government's authority to prosecute crimes committed on Indian reservations. This decision has been cited in numerous subsequent cases involving the federal government's power to regulate activities on Indian reservations.

In the dissenting opinion of Marshall v. United States, Justice William O. Douglas argued that the majority's decision was a violation of due process and an infringement on the rights of individuals to be free from unreasonable searches and seizures as guaranteed by the Fourth Amendment. He noted that there had been no showing that any evidence obtained through wiretapping would have been inadmissible at trial if it had not been obtained illegally, thus making its admission unconstitutional under established precedent. Furthermore, he argued that allowing such evidence to be admitted into court proceedings could lead to further abuses by law enforcement officials who may seek out illegal means for obtaining information or evidence against suspects without fear of repercussions or consequences for their actions.