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.

were decided the Court comprised these ten members (this was due to the Tenth Circuit Act of 1863, expanding the Court's membership from nine to ten justices, to date the largest number of active justices in its history): Ex parte Vallandigham, 68 U.S. (1 Wall.)

243 (1864) is a case involving a former congressman, Clement Vallandigham of Ohio, who had violated an Army order against the public expression of sympathy for the Confederate States and their cause.

On appeal, the Supreme Court issued a unanimous ruling refusing to address Vallandigham's main argument that the military tribunal lacked jurisdiction to try him.