The Supreme Court is established by Article III, Section 1 of the Constitution of the United States, which says: "The judicial Power of the United States, shall be vested in one supreme Court .

The size of the Court is not specified; the Constitution leaves it to Congress to set the number of justices.

To prevent President Andrew Johnson from appointing any justices, a hostile Congress passed the Judicial Circuits Act of 1866, eliminating three of the 10 seats from the Supreme Court as they became vacant, and so potentially reducing the size of the court to seven justices.

Newspaper publisher McCardle circulated "incendiary" articles advocating opposition to the Reconstruction laws enacted by Congress.

McCardle pursued a writ of habeas corpus in a Circuit Court in Mississippi, where he was unsuccessful.

After the case was argued but before an opinion was delivered, Congress suspended the Supreme Court's jurisdiction over the case, exercising powers granted under Article III, section 2 of the US Constitution to limit the appellate jurisdiction of the Supreme Court.

The Court held that the Constitution did not permit states unilaterally to secede from the Union, and that the ordinances of secession and all acts of legislatures in seceding states intended to give effect to such ordinances were void.