McClure 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 man named William McClure, who was charged with the illegal possession of whiskey. The evidence used to convict him was obtained through a search of his home without a warrant. The Supreme Court ruled in favor of McClure, holding that the evidence obtained through the illegal search and seizure was inadmissible in court. The Court reasoned that the Fourth Amendment of the United States Constitution protects citizens from unreasonable searches and seizures, and that the evidence obtained through the illegal search and seizure was in violation of this amendment. The Court also held that the exclusionary rule applied in this case, meaning that any evidence obtained through an illegal search and seizure was inadmissible in court. This case established an important precedent in criminal law, as it established the exclusionary rule and made it clear that evidence obtained through an illegal search and seizure was inadmissible in court. This ruling has been used in numerous cases since then, and has been an important part of criminal law in the United States.

Justice Field delivered the dissenting opinion in McClure v. United States, arguing that Congress had no authority to pass a law that would allow for the forfeiture of property without due process of law. He argued that such an act was unconstitutional and violated both the Fifth Amendment's protection against deprivation of life, liberty or property without due process as well as Article I Section 9 which states "No Bill of Attainder or ex post facto Law shall be passed." Justice Field further noted that even if Congress did have this power it should not be exercised lightly and only when absolutely necessary for public safety. In his view, there was no evidence presented by either party to show why such drastic measures were needed in this particular case and thus he concluded with a strong dissent from the majority decision.