Tobey v. Leonards was a case heard before the United States Supreme Court in 1864. The dispute arose when William Tobey, an administrator of the estate of his deceased brother-in-law, sued John and Mary Leonard for failing to pay him money owed from a promissory note that had been signed by them both. The Leonards argued that they were not liable because their signatures on the note had been forged by another party without their knowledge or consent. The Supreme Court held that since there was no evidence presented at trial indicating fraud or collusion between Tobey and any other person involved with forging the signature, it could be assumed that he acted in good faith when accepting payment from the Leonards based on what appeared to be validly executed documents. Therefore, they were found liable for repayment of all monies due under the terms of said promissory note regardless if their signatures were actually forged or not as long as it did not appear otherwise fraudulent at time of acceptance by Tobey himself.

In Tobey v. Leonards, the Supreme Court was asked to decide whether a contract between two parties could be enforced if it had been made in violation of a state law prohibiting such contracts. The majority opinion held that the contract was not enforceable because it violated public policy and thus should not be recognized by courts of justice. However, Justice Field dissented from this decision on the grounds that there were no clear legal principles or precedents which prohibited enforcement of such contracts and that allowing them would promote fairness among contracting parties who have acted in good faith. He argued further that refusing to recognize these agreements would lead to injustice as one party may suffer loss due to their reliance on another's promise without any remedy available for recovery. Ultimately, Justice Field concluded that while states are free to enact laws regulating certain types of contracts, they cannot prevent individuals from entering into valid agreements with each other even if those agreements violate existing statutes or regulations unless specifically provided for by statute or judicial precedent.