I respectfully disagree. The War for Southern Independence was exactly that. About 71% of eligible voters in Texas voted for secession. That meant the people decided their course of action -albeit a course of action that was denied to them.
It depends on your perspective. The north most certainly looked at it as a civil war. Lincoln repeatedly used the phrase “civil war.” He used it in the Gettysburg Address. It was common phraseology for the war in the north and they won. The victors write the history books. It’s real easy to re-write history 150 years later and say “well, technically that wasn’t a civil war.” Bottom line is this-they thought it was at the time. Those people LIVING THROUGH IT said it was. So, you and I can rewrite history if we want, but it doesn’t change what they said it was. They said it was a civil war...which is why we call it the Civil War.
By force, not by black letter law. It's a moot point now, of course.