What principle did South Carolina use to justify secession at the start of the Civil War?

The declaration stated the primary reasoning behind South Carolina's declaring of secession from the U.S., which was described as "increasing hostility on the part of the non-slaveholding States to the Institution of Slavery".

Explanation:

HOPE THIS HELPS ;}

there are hundreds of postives ways to unite a country with another country here are a   few

1 peace treaty's peace treatys

are basically a document signing a allliance with one country and another.

2 gift

what i mean by this is for example how the french gave the americans the statue of libery a gift of peace.

i think the answer is d