In Williams v. United States, the Supreme Court was asked to decide whether a defendant could be convicted of a crime if the evidence presented at trial was obtained through an illegal search and seizure. The defendant, Williams, was convicted of possession of a firearm in violation of the National Firearms Act. The evidence used to convict him was obtained through a search of his home without a warrant. The Supreme Court held that the evidence obtained through the illegal search and seizure was admissible in court. The Court reasoned that the Fourth Amendment, which protects against unreasonable searches and seizures, does not provide a remedy for the exclusion of evidence obtained through an illegal search and seizure. The Court further reasoned that the exclusionary rule, which would have excluded the evidence, was not applicable in this case because the search and seizure was conducted by federal officers, not state officers. The Court concluded that the evidence obtained through the illegal search and seizure was admissible in court and that Williams could be convicted of the crime. The Court's decision established that the exclusionary rule does not apply to searches and seizures conducted by federal officers.

Justice Harlan delivered the dissenting opinion in Williams v. United States, arguing that Congress had no authority to pass a law which allowed for the forfeiture of property used to commit an offense against the United States. He argued that such a law was unconstitutional because it violated due process and exceeded Congressional power under Article I, Section 8 of the Constitution. According to Justice Harlan, this provision only gave Congress limited powers over certain enumerated offenses and did not include any authority over forfeitures or punishments related to those offenses. Furthermore, he argued that if Congress were given such broad power then it could potentially punish individuals without trial or conviction by taking away their property through forfeiture laws. In conclusion, Justice Harlan believed that allowing for these types of forfeitures would be an unjust violation of individual rights and should not be permitted under our constitutional system.