Ex parte McCardle was a United States Supreme Court case that dealt with the power of the federal government to suspend the writ of habeas corpus. The case arose when William McCardle, a newspaper editor in Mississippi, was arrested by federal troops for publishing articles critical of Reconstruction policies. McCardle sought a writ of habeas corpus from the Supreme Court, arguing that his arrest was unconstitutional. The Supreme Court held that the federal government had the power to suspend the writ of habeas corpus in times of rebellion or invasion. The Court reasoned that the power to suspend the writ was necessary to protect the nation from enemies, both foreign and domestic. The Court also held that the suspension of the writ was a political question, and thus not subject to judicial review. The decision in Ex parte McCardle was controversial, as it limited the power of the Supreme Court to review the actions of the federal government. The decision was later overturned by the Supreme Court in the case of Ex parte Milligan, which held that the writ of habeas corpus could not be suspended in times of peace.

In Ex Parte McCardle, the Supreme Court was asked to decide whether a federal court had jurisdiction over a case involving an individual who challenged the constitutionality of Reconstruction Acts passed by Congress. The majority opinion held that because Congress had reserved for itself the power to review and revoke any decision made by a lower court in such cases, it did not have jurisdiction. In his dissenting opinion, Justice Field argued that this interpretation of Congressional authority would allow them to effectively nullify judicial decisions whenever they disagreed with them. He further argued that if this were allowed, then no one could be sure their rights would be protected under law since Congress could always step in and reverse any decision they didn't like. Furthermore, he noted that while there may have been some instances where it was necessary for Congress to intervene due to extraordinary circumstances or emergencies, these should remain rare exceptions rather than become common practice as suggested by the majority's ruling.