Falk v. Moebes was a United States Supreme Court case that addressed the issue of whether a state court could enforce a contract that was in violation of a federal statute. The case involved a contract between the plaintiff, Falk, and the defendant, Moebes, in which Moebes agreed to pay Falk a certain amount of money for the sale of a piece of property. The contract was in violation of a federal statute that prohibited the sale of property for more than its appraised value. The Supreme Court held that the state court could not enforce the contract because it was in violation of the federal statute. The Court reasoned that the federal statute was a valid exercise of Congress' power to regulate commerce, and that the state court could not enforce a contract that was in violation of a federal statute. The Court also noted that the state court could not enforce a contract that was in violation of public policy. The Court's decision in Falk v. Moebes established that state courts must abide by federal statutes and cannot enforce contracts that are in violation of federal statutes. This decision has been cited in numerous cases since then, and it has been used to support the principle that state courts must abide by federal law.

In Falk v. Moebes, the United States Supreme Court was tasked with determining whether a state court could enjoin an individual from collecting on judgments obtained in another state. The majority opinion held that such action would be unconstitutional as it violated the Full Faith and Credit Clause of the Constitution which requires states to give full faith and credit to public acts, records, and judicial proceedings of other states. Justice Field dissented from this decision arguing that while he agreed with much of what was stated in the majority opinion, he did not believe that Congress had intended for all judgments rendered by one state to be enforced by any other without regard for their validity or legality under local laws. He argued further that allowing individuals to collect on foreign judgments regardless of their legal standing within a given jurisdiction would lead to chaos as different jurisdictions have vastly different laws governing contracts and obligations between parties.