Question

Why did the Confederate states believe they were justified in seceding?
Ms. Sue
The Confederates believed that they were following the spirit of the U.S. Declaration of Independence. In addition the Constitution does not expressly forbid secesion.

http://www.ushistory.org/declaration/document/index.htm
physics
the confederates also thought that if they had a choice to be a united nation, they also had a choice to leave it.