Millingar v. Hartupée was a United States Supreme Court case that addressed the issue of whether a state court could enforce a contract made in another state. The case involved a contract between two parties, Millingar and Hartupée, in which Millingar agreed to pay Hartupée a certain sum of money in exchange for a certain amount of cotton. Hartupée sued Millingar in a state court in Georgia, where the contract was made, for breach of contract. Millingar argued that the state court did not have jurisdiction to enforce the contract because it was made in another state. The Supreme Court held that the state court did have jurisdiction to enforce the contract. The Court reasoned that the contract was valid and enforceable in the state where it was made, and that the state court had the power to enforce it. The Court also noted that the contract was not contrary to the public policy of the state in which it was made, and that the parties had the right to choose the forum in which to litigate the dispute. The Court's decision in Millingar v. Hartupée established that a state court can enforce a contract made in another state, provided that the contract is valid and enforceable in the state where it was made and that it is not contrary to the public policy of the state. This decision has been cited in numerous subsequent cases and has become an important precedent in contract law.

In Millingar v. Hartupée, the Supreme Court was asked to decide whether a contract between two parties could be enforced when it had been made in violation of an existing state law. The majority opinion held that the contract should not be enforced because it violated public policy and thus was voidable at the option of either party. Justice Field dissented from this decision, arguing that contracts are generally binding upon both parties unless they violate some fundamental principle of justice or morality or conflict with positive laws enacted by Congress or a state legislature. He argued that since there was no such conflicting law in this case, then the contract should have been upheld as valid and enforceable despite its illegality under state law. Furthermore, he argued that if courts were allowed to invalidate contracts based on their own notions of public policy rather than actual laws passed by legislatures, then contractual obligations would become uncertain and unreliable for all citizens who enter into them.