Marshall v. United States was a Supreme Court case that addressed the issue of whether a defendant could be convicted of a crime if the evidence used to convict them was obtained through an illegal search and seizure. The case involved a defendant, Marshall, who was charged with possession of stolen goods. The evidence used to convict Marshall was obtained through a search of his home without a warrant. Marshall argued that the evidence should be excluded from his trial because it was obtained illegally. The Supreme Court ruled in favor of Marshall, holding that evidence obtained through an illegal search and seizure could not be used to convict a defendant. The Court reasoned that the Fourth Amendment of the Constitution protects citizens from unreasonable searches and seizures, and that the exclusionary rule should be applied to prevent the government from using illegally obtained evidence to convict a defendant. The Court also held that the exclusionary rule should be applied even if the evidence was obtained in good faith. This case established the exclusionary rule, which is still used today to protect citizens from unreasonable searches and seizures. The exclusionary rule prevents the government from using illegally obtained evidence to convict a defendant, and it is an important part of the Fourth Amendment's protection of citizens' rights.

Justice Field delivered the dissenting opinion in Marshall v. United States, arguing that Congress had exceeded its authority under the Constitution when it passed a law allowing for criminal prosecution of those who committed offenses against Native Americans on reservations. He argued that while Congress has broad powers to regulate commerce with foreign nations and among states, this power does not extend to regulating internal affairs within a state or territory. Furthermore, he noted that if such regulation were allowed then any crime could be prosecuted by federal authorities regardless of where it was committed and without regard for local laws or customs. Justice Field concluded his dissent by stating that "the right of self-government is an inherent one which cannot be taken away from them [Native Americans] except as punishment for some great wrong."