Gregory v. Morris 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 two individuals, Morris and Gregory, in which Morris agreed to pay Gregory a certain amount of money in exchange for Gregory's services. The contract was made in violation of a state statute that prohibited such contracts. 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 without consideration or that were otherwise unfair. The Court's decision in Gregory v. Morris 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 has been used to support the idea that state courts should not enforce contracts that are made in violation of state law.

Justice Field delivered the dissenting opinion in Gregory v. Morris, arguing that a contract between two parties should not be voided simply because one of them was mistaken about a fact related to the agreement. He noted that while it is true that contracts made under false pretenses are voidable, this case did not involve any fraud or misrepresentation on either side; instead, both parties were honestly mistaken about an important detail regarding their agreement. Furthermore, he argued that if such mistakes could invalidate contracts then no agreements would ever be secure since all human knowledge is imperfect and subject to error. In conclusion, Justice Field believed there was no legal basis for voiding the contract in question and urged his colleagues to reverse the lower court's decision so as to protect innocent parties from being unfairly deprived of their contractual rights due solely to honest errors or misunderstandings.