Wallach et al. v. Van Riswick was a United States Supreme Court case that dealt with the issue of whether a contract between two parties was valid. The case involved a contract between Wallach and Van Riswick, in which Wallach agreed to pay Van Riswick a certain sum of money in exchange for a certain piece of land. Wallach argued that the contract was invalid because it was not in writing, while Van Riswick argued that the contract was valid because it had been partially performed. The Supreme Court ultimately sided with Van Riswick, ruling that the contract was valid and enforceable. The Court held that a contract does not need to be in writing in order to be valid, and that partial performance of a contract can be sufficient to establish its validity. The Court also noted that the parties had acted in good faith and that the contract was not unconscionable. The Court thus held that the contract was valid and enforceable, and that Wallach was obligated to pay Van Riswick the sum of money specified in the contract.

In Wallach et al. v. Van Riswick, the Supreme Court was tasked with determining whether a contract between two parties that had been made in California and then subsequently performed in New York could be enforced by a court of law in New York State. The majority opinion held that such contracts were not enforceable under the laws of either state, as they did not meet the requirements for an interstate contract set forth by Congress at the time. Justice Field dissented from this decision, arguing that while it is true that Congress has authority to regulate interstate commerce and thus can determine which contracts are valid across states lines, there is no indication here that Congress intended to limit or prohibit enforcement of these types of contracts between private individuals when both states involved have agreed to recognize them as valid agreements. He further argued that since neither party raised any objection during performance or attempted to avoid their obligations under this agreement until after its completion, it should be considered binding on both sides regardless of where it was formed or performed