And you’ve missed the historical facts completely. The Fed was not trying to force the states to eliminate slavery and Lincoln stated that he did not have the power to do that while the states were all a part of the union under the Constitution. He noted that it was not an issue that the Fed could rule on. If it was, Dred Scott would have been thrown out even after the SC decision. Lincoln knew that any federal ruling forcing abolition on states within the union was unconstitutional, just like obamacare is unconstitutional. Now, once the southern states foolishly seceded and stated that they were seceding over slavery, they no longer had the protection of the Constitution. Even with that, Lincoln did not declare emancipation for several years in hopes of pulling the south back and ending the war.
It was all about slavery, and states rights was a post-defeat excuse for the southern leadership to take heat off of them over why they ruined their states over an “asset” only a few (of them) owned. State’s Rights is another fine piece of democrat mythology/propaganda.
The North was not asserting any power over state rights to hold slaves. The North did assert that the secessionist states had no right to secede, over slavery or for any other excuse.
Slavery could have been abolished. It would have taken a constitutional amendment (3/4s of the states).