Halsted v. Buster was a United States Supreme Court case that addressed the issue of whether a state court could enforce a contract that was made in another state. The case involved a contract between two parties, Halsted and Buster, in which Halsted agreed to pay Buster a certain amount of money for the sale of a horse. Buster sued Halsted in a state court in New York for breach of contract, and Halsted argued that the contract was invalid because it was made in another state. The Supreme Court held that the state court had the authority to enforce the contract, as the contract was valid and enforceable under the law of the state in which it was made. The Court also held that the state court had the authority to enforce the contract even though it was made in another state, as long as the contract was valid and enforceable under the law of the state in which it was made. This decision established the principle that a state court can enforce a contract that was made in another state, as long as the contract is valid and enforceable under the law of the state in which it was made.

In Halsted v. Buster, the Supreme Court was asked to decide whether a contract between two parties could be enforced when it had been made without consideration and in violation of a state statute. The majority opinion held that the contract was unenforceable because it lacked consideration and violated public policy as expressed by the state statute. Justice Field dissented from this decision, arguing that while contracts lacking consideration are generally not enforceable, there were exceptions to this rule which should apply in this case. He argued that if one party had already performed their part of the agreement then they should be able to recover damages for breach of contract even if no additional consideration existed at the time of formation or enforcement. Furthermore, he argued that since both parties agreed on terms before any performance occurred then those terms should still stand regardless of any violations against public policy or statutes enacted after formation but prior to enforcement