Kelly v. Crawford is a United States Supreme Court case from 1866 that dealt with the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. The case arose when a prisoner, John Kelly, was held in a federal prison in the state of Georgia. Kelly sought a writ of habeas corpus from the state court, which the court granted. The federal government then appealed the decision to the Supreme Court. The Supreme Court held that the state court did not have the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. 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 noted that the writ of habeas corpus was a fundamental right, and that the state court should not be allowed to interfere with the federal government's power to imprison individuals. In conclusion, the Supreme Court held that the state court did not have the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. 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 noted that the writ of habeas corpus was a fundamental right, and that the state court should not be allowed to interfere with the federal government's power to imprison individuals.

In the case of Kelly v. Crawford, Justice Field wrote a dissenting opinion in which he argued that the majority's decision was wrongfully based on an interpretation of state law rather than federal law. He asserted that Congress had exclusive authority to regulate commerce between states and territories, and thus any attempt by a state legislature to do so would be unconstitutional. Furthermore, he argued that even if it were permissible for a state legislature to pass such laws, they must still comply with the Constitution's Commerce Clause which requires uniformity among all states when regulating interstate commerce. As such, Justice Field concluded that since California had not provided equal protection under its own statute as required by the Commerce Clause then their legislation was invalid and should have been struck down by the court.