Keely v. Sanders 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, Keely and Sanders, in which Sanders agreed to pay Keely a certain amount of money for the sale of a horse. Sanders failed to pay the agreed-upon amount, and Keely sued in a state court in Mississippi. Sanders argued that the contract was made in Alabama and that the Mississippi court had no jurisdiction to enforce it. The Supreme Court held that the Mississippi court had jurisdiction to enforce the contract. The Court reasoned that the contract was valid and enforceable in the state where it was made, and that the Mississippi court had the power to enforce it. The Court also noted that the contract was not contrary to the public policy of either state, and that the Mississippi court had the power to enforce contracts made in other states. The Court's decision in Keely v. Sanders established that state courts have the power to enforce contracts made in other states, provided that the contract is valid and enforceable in the state where it was made and that it is not contrary to the public policy of either state. This decision has been cited in numerous subsequent cases involving the enforcement of contracts made in other states.

Justice Field delivered the dissenting opinion in Keely v. Sanders, a case involving an action of ejectment brought by the plaintiff against defendants for land located in Texas. Justice Field argued that although it was true that Texas had been annexed to the United States and admitted as a state after this suit was commenced, he did not believe this should affect its outcome because at the time of commencement, Texas was still an independent nation with full power to pass laws affecting property within its borders. He further noted that even if annexation were considered relevant here, there would be no reason why any change should take place since both parties were citizens of Texas when they entered into their agreement regarding title to said land and thus could not have anticipated or foreseen such a change occurring during litigation. Finally, Justice Field concluded by noting that while Congress may have had authority over certain matters related to annexation (such as foreign relations), it did not possess any power which would allow them to interfere with private contracts between individuals living within those territories prior thereto - especially where such interference might result in one party being unjustly enriched at another's expense.