The Declaration of Independance was a list of grievances showing the right of the colonies to fight for sovereignty against "absolute despotism." The Union certainly had not inflicted any of those depradations on the South. So by this standard, the South certainly was in rebellion. Check out
http://www.ushistory.org/declaration/document/index.htm
On the other hand we all know the New England states wanted to secede during the War of 1812. Though it didn't get anywhere, the case had merit and was used later. Then there were the mormons.
Now about Braxton Bragg...
2nd Lt. Beno
5/2/I AoP
USA