Roderick Long writes in Shades of Grey (and Blue):

To their joint discredit, both Union and Confederacy waged war against the principle of free association. Southern rebels claimed the right to exit the Union, but hypocritically denied slaves the same right to exit the plantation.

President Lincoln, for his part, stated plainly that his “paramount Object” was “to save the Union,” and “not either to save or to destroy slavery.” If there had been no slaves, Lincoln would have sought to crush secession anyway. (And with conscripted troops!)

North and South alike, then, championed compulsory over free association. It is difficult to escape the conclusion that the Civil War was an unjust war on both sides.