Ex parte Harmon was a United States Supreme Court case that dealt with the issue of whether or not an individual could be held liable for debts incurred by another person. The plaintiff, John W. Harmon, had been sued in a state court on behalf of his father-in-law's estate for payment of certain debts and damages due to the father-in-law's negligence. Mr. Harmon argued that he should not be held responsible because he did not sign any contract or agreement related to the debt and therefore could not be legally bound by it. The Supreme Court ultimately ruled in favor of Mr. Harmon, finding that since he had no knowledge nor involvement in incurring the debt, there was no legal basis upon which to hold him accountable for it; thus establishing precedent regarding liability when one is unaware they are being made party to a contract or agreement without their consent or knowledge

In Ex Parte Harmon, the Supreme Court was asked to decide whether a state court had jurisdiction over an Indian tribe. The majority opinion held that the state court did have jurisdiction and could proceed with its case against members of the tribe. Justice McLean dissented from this decision, arguing that it violated both federal law and treaties between tribes and states. He argued that Congress alone has authority to regulate relations between Indians and non-Indians, as well as exclusive power to make laws concerning Indian affairs. Furthermore, he noted that any treaty made by a state with an Indian nation must be approved by Congress before it can take effect; thus, no such treaty existed in this case which would give the state court jurisdiction over tribal matters. Justice McLean concluded his dissent by asserting that allowing states to exercise control over tribes would lead only to injustice for Native Americans who are unable or unwilling to protect their own interests due to lack of knowledge about legal proceedings or resources necessary for litigation