In the United States v. Eckstein case of 1911, the Supreme Court examined whether a contract for the sale of goods was enforceable when it involved an illegal activity. The defendant, Eckstein, had entered into a contract with another party to sell cotton linters (a byproduct of cotton production) which were to be used in manufacturing explosives for Russia during its war with Japan - an act that violated U.S neutrality laws at that time. When Eckstein failed to deliver all agreed upon goods and refused to refund payments made, he was sued by his business partner who sought enforcement of their agreement or compensation for losses incurred due to non-delivery. The Supreme Court ruled against enforcing such contracts as they involve illegal activities contrary to public policy. It held that courts should not aid those engaged in unlawful acts nor grant them any relief based on agreements related thereto; hence no recovery could be obtained from such transactions even if one party defaults or fails in performance as promised under the contract terms.

In the dissenting opinion for United States v. Eckstein, Justice Holmes disagreed with the majority's decision to uphold a conviction based on evidence obtained through an illegal search and seizure. He argued that this violated the Fourth Amendment rights of the defendant, which protect against unreasonable searches and seizures without probable cause or a warrant. Holmes believed that allowing such evidence to be used in court would set a dangerous precedent, undermining citizens' constitutional protections and potentially leading to abuses of power by law enforcement authorities. Furthermore, he contended that upholding this conviction contradicted previous Supreme Court rulings which had established clear guidelines for what constitutes legal search procedures under the Constitution.