Chapman v. Brewer, Assignee 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 state statute. The case involved a contract between Chapman and Brewer, in which Chapman agreed to pay Brewer a certain sum of money in exchange for Brewer's assignment of a debt owed to him by a third party. The contract was made in violation of a state statute that prohibited the assignment of debts. The Supreme Court held that the state court could not enforce the contract because it was made in violation of the state statute. The Court reasoned that the state statute was a valid exercise of the state's police power and that the state had the right to protect its citizens from contracts that were made in violation of its laws. The Court also noted that the state had the right to protect its citizens from contracts that were made in violation of its laws. The Court concluded that the state court could not enforce the contract because it was made in violation of the state statute.

Justice Field delivered the dissenting opinion in Chapman v. Brewer, Assignee. He argued that the court should have followed precedent set by prior cases and held that a contract between two parties cannot be modified without their mutual consent. In this case, he believed that the defendant had not agreed to any modification of his original contract with plaintiff; therefore, it was still valid and enforceable under law. Furthermore, Justice Field noted that even if there were some evidence of an agreement to modify the terms of the contract between plaintiff and defendant, such an agreement would not be binding on either party unless they both consented to it in writing or orally before witnesses who could testify as to its validity. Therefore, he concluded that since no such written or oral agreement existed here, plaintiff's claim for breach of contract must fail because her rights under her original contract remained intact despite any alleged modifications made after its execution date.