I leap to the conclusion that you believe Lincoln and his troops fought the war to “free the slaves.”
For the purpose of this post, let's stipulate that the purpose of Lincoln's war was, indeed, to free the slaves.
That's a problem for anyone that claims to support the original United States Constitution.
Although some will occasionally deny it, the original U.S. Constitution included slavery. The founders provided an amendment process to peacefully change the Constitution but did not provide a mechanism for the President to use troops to violently overthrow the Constitution and its slavery provisions.
After the House Divided speech many southerners believed Lincoln, if elected, would use the U.S. military to attack the South and to violently overthrow the United States Constitution.
Maybe he did.
Won’t agree to your stipulation. Lincoln’s objective was to restore the Union. Freeing the slaves in the States in rebellion was a very shrewd political move.
The original Constitution acknowledged the existence of slavery in the country. It did not mandate slavery. It did not require slavery. There was nothing in the Constitution that prevented the outlawing of slavery by any state in the Union.
Once war began, the enemy was not afforded any protection of the Constitution because they were the ones that repudiated the Constitution. They were the ones that voluntarily withdrew from the Republic that was established by that Constitution. Lincoln as CinC was allowed the leeway to destroy slavery in the States in rebellion. The Constitution no longer applied to any state in the Confederacy. Outlawing slavery in the States of Rebellion is not un Constitutional because the Confederacy was no longer subject to the Constitution by their own actions. He did not outlaw slavery in any state that remained loyal to the Constitution and the Republic.