Was it illegal for the South to break-away? Q #3

I'm reaching out here to the Civil War Researchers. I'm doing research for an ebook. I'd appreciate any info on Sunday battles. If used in publication, I'll of course cite you as a source. Email me at chris@greensblueandgray.com. Thanks in advance.

Now, here we go with question #3 posed by Benjamin J. Stein back in October 2003 in “The American Spectator”. “Preserving the Civil War” was the title of his three page essay that asked ten, most often, provocative, questions about the beginning of the conflict, ramifications of this and that decision, and the 'what might have beens' of it all. I plan to keep the article, and I want to continue sharing it here:

#3


"Why was it legal for the colonies to rebel against Britain but not for the South to rebel against the North?

Again, I assume slavery was and is horrible and disgusting and a crime against humanity. But it was legal under the U.S. Constitution, so why was it allowable to wage a moral crusade killing six hundred thousand men to end it and to compel the slave states back into the Union? If popular sovereignty and right to self-determination mean anything, why did they not mean something in North America? Clearly the South (most but not all of it) wanted to be separate. Why was war the response to popular sovereignty? Or did the Southern firebrands force it on the North? If so, could the North have walked away from the fight? And, again, I am convinced that slavery was thoroughly horrible. But so is war."