I am not a big fan of the Civil War, a needless, horrible castrophe, but a constitutional amendment requires 3/4’s of the states and 2/3 of the Senate to approve it. The South cheered the Dred Scott decision, not realizing that the chain of events it unleashed.
Their economic output was based on the usage of slave labor. People defend their rice bowls no matter what.
The problem was not so much with the Dred Scott decision, which was mostly correct from a legal technicality perspective, it is the fact that states who's culture had changed such that they no longer wished to abide by the agreement they had signed.
They were trapped by a law that said they had to enforce slavery whether they liked it or not, and their moral preferences.
What they did was ignore the law, and then made up excuses for refusing to enforce it. They knew they didn't have the clout to get an amendment passed, and so they simply practiced "Irish Democracy" on the issue.