My law professors were very squirrely about laying out exactly what happened after the war and the constitutionality of it. Everybody agreed to the 13th amendment to abolish slavery. The Southern elected representatives took up their seats again and voted for it and Southern states ratified it. Everybody well understood slavery was abolished and gone and that had been decided - and everybody accepted that.
Then I was taught that Radical Republicans "laid a trap" in the proposed 14th and 15th amendments basically annihilating the rights of the states and making them little more than administrative conveniences for the federal government AND dictating who each state could elect as a representative. The Southern states refused to pass these. THEN the Radical Republicans using raw military force declared the elected Southern representatives were somehow not valid and imposed military occupation on the Southern states. They also disenfranchised the vast majority of the voters in the Southern States.
They prosecuted the war on the argument that the Southern states had never lawfully left the union.....then turned right around 180 degrees and said the Southern states were "out" and had to agree to the 14th and 15th amendments to get back "in"....even though they were never out. Somehow.
I asked what article of the Constitution allowed ANY OF THIS and they hemmed and hawed and never gave a straight answer. Basically their answer amounted to "Well.....it was done so we have to accept it now". Not one bit of any of it was even remotely constitutional. Those amendments were never lawfully passed. The federal government does not get to disenfranchise voters in a state nor dictate whom they may elect nor set terms under which unconstitutional tyrannical conditions imposed on them will be lifted.
This is why I say the original constitution died at Appomattox. It did.
I make this argument whenever this topic comes up. Over at Instapundit, I got a comment from Glenn Reynolds, who is the law professor that runs the place.
When I pointed out the 13th, 14th and 15th amendments were not lawfully ratified, he mentioned that this issue has long been discussed in academic circles. Apparently there is a body of legal professors that agree with the point.