It did not come before full court under Chief Justice Marshall, it has never come before the full Supreme Court under any Chief Justice. And the only time a single justice can issue a ruling by himself is if he is sitting on the circuit court bench, as Taney was.
It was proper that the writ be issued by Chief Justice Taney. This was an emergency matter since a habeas corpus writ issued by the Maryland District Court had already been disobeyed by the army that same month. The District Court was powerless to confront the army.
Habeas corpus had been suspended in the Baltimore area by the president, so Taney's issuing the writ was invalid.
Yes, suspending the writ of habeas corpus MEANS that a judge’s order to d=relase someone is invalid.
Habeas has actually been before the Supreme Court several times, and yes it did come before John Marshall in 1807.
It also came before Chief Justice Chase in 1866, Chief Justice Stone in 1942, Chief Justice Rehnquist in 2004, and Chief Justice Roberts in 2006.
DECISION.
Ex Parte.......................} Before the Chief Justice of the
.....................................} Supreme Court of the United
John Merryman.........} States at Chambers.
I added dots to preserve the spacing of the original. At Chambers rulings are rulings of the Justice as a Justice of the Supreme Court. The signature on the ruling is "R. B. Taney, Chief Justice of the Supreme Court"