Cadman v. Peter 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, Cadman and Peter, in which Cadman agreed to pay Peter a certain sum of money in exchange for a certain amount of land. The contract was made in the state of New York, but Peter sued Cadman in a court in the state of Pennsylvania. The Supreme Court held that the Pennsylvania court did not have the authority to enforce the contract because it was made in another state. The Court reasoned that the contract was made in New York and was therefore subject to the laws of that state. The Court also noted that the contract was not a matter of interstate commerce, and thus the Pennsylvania court did not have the authority to enforce it. The Court's decision in Cadman v. Peter established the principle that a state court cannot enforce a contract that was made in another state. This principle has been applied in numerous cases since then, and it is an important part of the law of contracts.

In the case of Cadman v. Peter, Justice Field delivered a dissenting opinion arguing that the majority's decision was wrongfully based on an erroneous interpretation of the law. He argued that under Missouri state law, which governed this case, it was clear that when two parties enter into a contract and one party fails to fulfill their obligations as agreed upon in the contract, then they are liable for damages incurred by the other party due to their breach of contract. The majority had ruled otherwise and held that no damages were owed because there had been no actual damage done; however Justice Field disagreed with this conclusion and argued instead that any failure to perform according to contractual terms constituted sufficient grounds for liability regardless of whether or not any actual damage occurred. In his view, if one party failed to meet its obligations under a validly formed agreement between two parties then they should be responsible for compensating those who have suffered losses as a result - even if those losses are only potential ones rather than tangible ones.