[retarmy]

4CJ wrote, “Actually secession is not prohibited - it's a reserved right (see the 10th). The states were the arbiters of federal power, not the federal government. “
You are correct that secession was a right, but as Restorer correctly pointed out, the southern states fired upon a federal military installation before the issue of secession was resolved by Congress. Since the military action preceded the legislative action, the states were in insurrection, not legal secession. Everything else fell apart from that act. Who knows how history would have been changed had the Confederate forces allowed the legitimate process to succeed?

[Restorer]

Your comment is well taken, except that Congress could not determine whether secession was Constitutional, inasmuch as the reps from the seceding states had left.

Anyway, the question was a legal/constitutional one, not a political one, and it would have been more appropriate to address it in the SC than in Congress. IMHO.

Except that the seceding states never attempted to do so.