Johnson v. Harmon was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner who was being held in a federal prison. The case arose when a prisoner, Johnson, was held in a federal prison in the state of Indiana. Johnson sought a writ of habeas corpus from the state court, claiming that he was being held in violation of the Constitution. The state court granted the writ, and Johnson was released from prison. The United States Supreme Court held that the state court did not have the authority to issue the writ of habeas corpus. The Court reasoned that the writ of habeas corpus was a federal power, and that the state court did not have the authority to interfere with the federal government's power to imprison individuals. The Court also held that the state court's decision to issue the writ was an unconstitutional interference with the federal government's power to imprison individuals. In conclusion, the United States Supreme Court held that the state court did not have the authority to issue the writ of habeas corpus to Johnson, and that the state court's decision was an unconstitutional interference with the federal government's power to imprison individuals.

Justice Field delivered the dissenting opinion in Johnson v. Harmon, arguing that the majority's decision was contrary to both law and equity. He argued that a contract between two parties should be enforced according to its terms, regardless of whether it is fair or not. In this case, he noted that there had been an agreement between Johnson and Harmon for the sale of land which included a provision for payment over time with interest on unpaid balances due at maturity. The majority held that such provisions were void under state law as usurious; however Justice Field disagreed with this conclusion because no evidence had been presented showing any violation of state laws regarding usury rates or other matters related thereto. Furthermore, he argued that even if such violations did exist they would only render the contract unenforceable by legal action but could not affect equitable relief since equity looks beyond mere technicalities when deciding cases involving contracts made in good faith without fraud or mistake on either side. Therefore, Justice Field concluded his dissent by stating his belief that justice demanded enforcement of the original agreement as written rather than allowing one party to benefit from their own breach while punishing another who has done nothing wrong