May v. Le Claire was a United States Supreme Court case that was decided in 1870. The case involved a dispute between two parties over the ownership of a piece of property in the state of Iowa. The plaintiff, May, claimed that he had purchased the property from the defendant, Le Claire, in 1867. Le Claire, however, argued that the sale was invalid because he had not received full payment for the property. The Supreme Court ultimately sided with May, ruling that the sale was valid and that May was the rightful owner of the property. The Court reasoned that Le Claire had accepted partial payment for the property and had not taken any action to reclaim it. Furthermore, the Court noted that Le Claire had waited three years before bringing the dispute to court, which was seen as an indication that he had accepted the sale. As a result, the Court held that May was the rightful owner of the property and that Le Claire had no legal claim to it.

In the case of May v. Le Claire, the Supreme Court was asked to decide whether a contract between two parties could be enforced even though it had been made in violation of a state law. The majority opinion held that the contract should not be enforced because it violated public policy and thus was voidable at either party's request. However, Justice Field dissented from this decision and argued that contracts are binding regardless of any violations they may have committed against state laws or public policy. He reasoned that if courts were allowed to invalidate contracts based on such considerations, then individuals would lack confidence in their ability to make agreements with each other without fear of them being overturned by judicial review. Furthermore, he argued that allowing states to interfere with private contractual arrangements would lead to chaos as different states adopted varying policies regarding what constituted valid contracts within their borders. Ultimately, Justice Field concluded that while certain types of illegal contracts should not be enforceable due to moral considerations or fraudulence, those which do not involve these elements should still remain legally binding despite any potential violations against state laws or public policy