But the point is, the Confederate States were not among "all the states". They had seceeded from the union and the Constitution no longer applied to them.
If you wish to argue that they had no right to seceed, you have to repudiate the Declaration of Independence. If the 13 Colonies had the right to seceed from England, then the southern states had the right to seceed from the US.
The colonies did not "secede" and they had no right under British Law to do so. They Rebelled which was their right under Natural Law when faced with oppression.
What oppression was the South facing in 1860?
No state can get out of the Union without the consent of the co-states.
Wishing it won't make it so.
Congress is charged in Article 1, section 8 with providing for the general welfare and common defense.
The Militia Act of 1792 was passed specifically because a situation might arise where United States laws might not be operating in one or more of the states. That act empowers and requires the president to use the military forces of the Union to ensure that the laws of the United States operate in all the states.
Your position is unsupportable.
Walt