Merritt v. Welsh was a United States Supreme Court case that addressed the issue of whether a state court could enforce a contract that was made in violation of a state statute. The case involved a contract between Merritt and Welsh, in which Merritt agreed to pay Welsh a certain amount of money for the sale of a horse. The contract was made in violation of a state statute that prohibited the sale of horses for more than a certain amount. The Supreme Court held that the state court could not enforce the contract because it was made in violation of the state statute. The Court reasoned that the state statute was a valid exercise of the state's police power, and that the state had the right to protect its citizens from contracts that were made in violation of the law. The Court also noted that the state had the right to protect its citizens from contracts that were made in bad faith or with the intent to defraud. The Court's decision in Merritt v. Welsh established that state courts could not enforce contracts that were made in violation of state statutes. This decision has been cited in numerous cases since then, and it has been used to support the idea that state courts should not enforce contracts that are made in violation of the law.

Justice Field delivered the dissenting opinion in Merritt v. Welsh, arguing that the majority's decision was an incorrect interpretation of the law and would lead to unjust results. He argued that a contract for personal services is not necessarily void because it does not specify a definite time period; rather, such contracts are valid as long as they do not violate public policy or any other laws. In this case, he believed that there was no evidence to suggest that either party intended their agreement to be limited by time or subject to termination at will. Furthermore, Justice Field noted that even if one party had attempted to terminate the contract without cause prior to its expiration date, they should still be held liable for damages caused by their breach of contract since it was never agreed upon between them beforehand. Finally, he concluded his dissent with an argument against allowing employers too much freedom when terminating employees' contracts before completion: "It is important...that employers shall have no power arbitrarily and capriciously [to] break up engagements which parties may enter into."