South Carolina had threaten to secede from the Union in the 1830's but Pres. Jackson threatened to lead the army himself, and the rebellion movement died. Would the movement of 1861 have been different had the South just starved the fort into submission or taken some other less direct method of taking control?
In other arguments the Supreme Court's ruling are quoted. One of the primary reasons for considering secession is that the Supreme Court itself is binding itself to previous decisions even when these decisions are blatantly unconstitutional. The concept of the Constitution being the ruling document has been forgotten by all three branches of the US government.