Babbitt v. Clark 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 federal statute. The case involved a contract between the plaintiff, Babbitt, and the defendant, Clark, for the sale of a tract of land in the state of California. The contract was made in violation of the California Land Act of 1851, which prohibited the sale of public lands without the approval of the state legislature. 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’s power to regulate the sale of public lands, and that the state court could not enforce a contract that was in violation of a federal statute. The Court also held that the state court could not enforce the contract because it was against public policy. The decision in Babbitt v. Clark established the principle that state courts cannot enforce contracts that are in violation of federal statutes. This principle has been applied in numerous cases since then, and it is an important part of the legal landscape today.

Justice Field delivered the dissenting opinion in Babbitt v. Clark, arguing that Congress had no authority to pass a law allowing for the sale of public lands without first obtaining consent from California. He argued that when California was admitted into the Union, it retained all rights and privileges as if it were an independent state, including its right to control land within its borders. As such, he believed Congress could not interfere with this right by passing legislation which allowed for sales of public lands without permission from California's legislature or people. Furthermore, Justice Field noted that even though some states may have ceded their claims over certain territories after admission into the Union (as happened with Texas), this did not mean they gave up their sovereignty over those areas forever; rather they only relinquished them temporarily until such time as Congress decided what should be done with them. Thus, he concluded that any attempt by Congress to sell off these lands without consulting either California or her citizens would be unconstitutional and invalidate any contracts made under such circumstances.