FIRST
Whether or not the Confederates committed treason depends on which parts of the Constitution's definition of treason you look at. You are correct that secession specifically is not prohibited. However, levying war against the United States and forming a confederation is prohibited within it. The Confederate states did both.
You have directed me to the Supreme Court as proof that the Confederate states did not commit treason and since your direction implies that you respect the Supreme Court on this issue, I will direct you to the same place, specifically the case of Sprott vs. United States.
The case you reference was heard in 1874, thirteen years after the act of secession was committed and nine years after Chief Justice Salmon P. Chase declared to President Lincoln that the Supreme Court could never uphold a treason conviction for any Confederate based on the fact that there was NOTHING in the Constitution at the time which made Secession illegal. As far as "taking up arms" is concerned, it was the US that launched an invasion of the CSA thus provoking the insuing war, this is irrefutable. Your premise here, regarding this 1874 decision, is supported quite flimsily by the remarks of one justice in a case which stemmed from a lawsuit initiated by a Southerner regarding lack of compensation for seized cotton. :shrug: This was not a Declaration of treason against the Confederates. If it were, then why was no one put on trial?
SECOND
One could argue that they levied war and formed a confederation as a separate entity and therefore, did not commit treason, but for that argument, I direct you to the Supreme Court again, specifically the case of Williams v. Bruffy:
To confirm this point of view, I also direct you to one Chief Justice Chase's own cases - Texas v. White:
First allow me to correct your biggest inconsistency in this statement: The Confederation was formed FIRST. THEN war insued. Placing these into the correct chronology then causes us to beg the question: "Which side initiated the war?" Claiming that the Confederacy was formed with the sole purpose of waging war against the United States is simply fallacious and could/would not have held up under legal scrutiny.
Regarding
Williams vs. Bruffy which was decided sixteen years AFTER Secession; it's sole function
was to nullify all laws, and "legal" property rights which had been established by the CSA during the war years. It served to basically, return legal jurisdiction to the Constitution and to the United States government. Most view this case as simply procedural when a conquering nation wishes to incorporate (or in this case, reincorporate) territory gained. :shrug:
THIRD
You have offered the pardon of Confederate leaders as proof that treason was not committed. However, I direct you to Lincoln's proclamation of these pardons as proof that it was treason. In that proclamation, Lincoln declared:
First, I never said anything about a pardon. My contention was that charges of treason against Confederates was never Constitutionally legal to begin with.
Most historians and legal experts would agree that Lincoln's proclamation of amnesty was pointless and more for PR and political expediency. I've already pointed out to you that Lincoln was told by the Chief Justice of the Supreme Court that charges of treason were not Constitutional in this case and would not stick. And this came from a Republican justice who had worked directly under Lincoln at one point.
Oh, and in reference to the partial statement from
Texas vs White which you boldened; wasn't the Court referring to the Military Board of Texas and not the entire Confederate government?