They would seek a ruling from the US Supreme court to avoid damage to the institutions and nation from whence they came. To prevent a Civil War. Pretty good reasons if the true intent of the confederates was to go in peace, don't you think?
At the risk of causing your head to explode, let me add something from one of those old meaningless documents you neo-rebs like to thumb your nose at
"Prudence indeed, will dictate that Governments long established should not be changed for light or transient Causes" -2nd Continental Congress July 4th 1776
What noble confederate Cause was there other than the protection and expansion of slave power?
The right of self-government.
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. That to secure these rights, Governments are instituted among Men, deriving their just Powers from the consent of the governed, -- That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness.
Once again, there was nothing to seek a ruling over. The seceding States had no grievance in regards to the legality of secession. If the other States objected to them excercising their right to secede, then they should have filed a grievance in regards to it. The seceding States had no grievance in regards to secession that would require them to even approach the Court over the issue.
At the risk of causing your head to explode, let me add something from one of those old meaningless documents you neo-rebs like to thumb your nose at: "Prudence indeed, will dictate that Governments long established should not be changed for light or transient Causes" -2nd Continental Congress July 4th 1776
LOL - No one is thumbing their noses at old documents, only at revisionists and propagandists who attempt to twist and misuse the words from those documents.