Rehnquist may disagree, and it is my understanding that he holds personally that the issue is debatable, but to say that the court has not ruled on it is to deny court precedent.
"The decision that the individual shall be imprisoned must always precede the application for a writ of habeas corpus, and this writ must always be for the purpose of revision that decision, and therefore appellate in its nature. But this point also is decided in Hamilton's case and in Burford's case. If at any time the public safety should require the suspension of the powers vested by this act in the courts of the United States, it is for the legislature to say so. That question depends on political considerations, on which the legislature is to decide. Until the legislative will be expressed, this court can only see its duty, and must obey the laws." - John Marshall for the majority, Ex Parte Bollman & Swartwout (1807)
Was the full court in session?
If you mean for Merryman, the ruling was a circuit court one. If you mean the supreme court, I do not know though the court can and has acted in extraordinary circumstances on appeals needing immediate attention, as would have been the case in this one.
As is his constitutional prerogative to do so.
It is his constitutional duty to operate within the constitutional process if he does not like a check imposed on his actions by another branch. That means having to appeal the decision. The Lincoln did not do so and therefore violated the constitutional process of the judiciary. The Supreme Court, by design, has no enforcement power over the executive branch.
The Supreme Court has no enforcement power per se over anything. It only rules on the matter. But it does have the authority to rule on the actions of the congress or the executive when they are in breach of the constitution.
The fact that Congress was not in session in April of 1861, (timing that I'm sure was planned by the Confederates when they ratcheted tensions by firing on Sumter) allows the President to invoke the Militia Act.
The militia act does not permit the president to suspend habeas corpus. Try again.
Members of congress were scattered across the continent from Maine to California and Oregon in April of 1861 and with transportation and communication of the day, and Congress only in session for 3 months a year, it was impossible to assemble them in time to deal with an emergency.
Difficult yes, but not impossible. Only two small population states were beyond a relatively easy journey to Washington, California and Oregon. The rest could have made it there.
That is why the first congress passed the Militia Act which gave the President very broad powers in a state of emergency.
But not the power to suspend habeas corpus, which standing court precedent says is for the legislature to decide including in times "the public safety should require the suspension" of the writ.
Rehnquist may disagree, and it is my understanding that he holds personally that the issue is debatable, but to say that the court has not ruled on it is to deny court precedent.
The court has ruled in Dred Scott and Plessey v. Furguson, to say nothing of Roe v. Wade. I guess you are coming down on the side of abortion on demand, simply because of court precedent. There are higher laws than U.S. law, but I digress.
Taney had no right deciding anything about Merryman. I found this online:
"Taney was aggressively pro-Southern. He has been described as a Jacksonian Unionist (Jackson appointed him), but his Unionism was not all that solid. In an 1856 letter to his son-in-law. Taney predicted the election of Fremont or Fillmore, and lamented that South would not successfully secede."
Taney went outside what he should have done in ruling on Merryman.
I don't know what Chief Justice Rehnquist's thought process in saying that the issue of the president's power to suspend the Writ has never yet been authoritatively decided.
But I know this whole thing comes down to his opinion versus yours. And your's is just as partisan as anything Taney ever did.
Walt