The Supreme Court said the rebellion had the same status under law a a foreign war. The president is commander in chief of the Armed Forces in time of war. The -law- of war allowed for the seizure of enemy property.
What the secessionists did was to liable themselves to presidential power in a way that would have been impossible in the normal course of administering the government. Slavery was clearly protected by the Constitution. Once they became de facto enemies of the United States, then the president's war powers overrode the protection for slavery.
THIS is why (and I think -you- know this) the EP only had effect in the areas outside of federal control. Slave holders in loyal areas and states were beyond the president's war power.
The slave power maladroitly lost in 4 years what they could have retained for generations.
Walt
Novel constitutional theory there, Walt. Someone declares war, and poof, the Constitution is altered, magically and instantaneously.
You didn't answer rustbucket's charge, that Lincoln exceeded the powers of his office. You just changed the subject and talked about something else, as if that were responsive to his charge.