In 1861, after Fort Sumter fell, the U.S. Army seized John Merryman, a Maryland citizen and state militia officer, and detained him in Fort McHenry, in Baltimore, Maryland. Merryman’s lawyers sought a writ of habeas corpus. After a hearing, Taney determined that the Army had violated the Constitution by seizing and detaining Merryman absent due process. Taney offered much flowing language—the sort which endears him to do-gooders and starry-eyed civil libertarians. But that is all that Taney did: He offered pieties in a judicial opinion. The reality is that Taney did not grant Merryman habeas corpus. In other words, Taney did not order the Army, or the commander at Fort McHenry (the named defendant in Ex parte Merryman), or the President, or anyone else to release Merryman from the Army’s prison. Now, perhaps the Army would not have obeyed any such a judicial order, but we will never know because Taney never issued one.
Further interesting thoughts at the link.