United States v. Knox is a United States Supreme Court case that was decided in 1881. The case involved a dispute between the United States and the estate of John Knox, a deceased merchant. The United States had seized a shipment of goods from Knox's estate, claiming that the goods were subject to forfeiture due to violations of the Tariff Act of 1846. The Supreme Court held that the goods were not subject to forfeiture because the Tariff Act did not apply to goods that had been imported prior to the passage of the Act. The Court also held that the United States had no right to seize the goods without first obtaining a court order. The decision in United States v. Knox established that the government cannot seize goods without first obtaining a court order. This decision has been cited in numerous subsequent cases involving the government's power to seize property. The decision also established that the government cannot retroactively apply laws to goods that were imported prior to the passage of the law. This decision has been cited in numerous subsequent cases involving the retroactive application of laws.

Justice Field delivered the dissenting opinion in United States v. Knox, arguing that the majority's decision was contrary to established precedent and would lead to an unjust result. He argued that Congress had not intended for a tax on distilled spirits to be imposed upon those who purchased them from another state, as it would amount to double taxation of goods already subject to taxes by their original state of origin. Furthermore, he noted that such a law could have far-reaching implications beyond this case and could potentially interfere with interstate commerce if other states were allowed similar authority over goods imported from other states. Finally, Justice Field argued that allowing such taxation would violate the Constitution’s Commerce Clause which grants exclusive power over interstate commerce solely unto Congress. In conclusion, Justice Field believed the majority’s ruling should be overturned due its potential negative consequences on both individuals and businesses alike across multiple states throughout America