How did the southern states that seeded justify leaving the union

The southern states who left the Union--later becoming the Confederacy--justified their action through slavery. The southerners used and relied on slaves whereas the northerners were primarily abolitionists. The Confederacy split from the Union in hopes to preserve slavery.

When South Carolina seceded from the Union in 1860, the main justification of secession was that southerners believed secession was the only way they could preserve their institution of slavery. Not all southerners supported secession, however, but those who did argued that because the southern states were a part of the Union, their rights should be respected by the federal government.