That's sophistry, and you probably don't know it.
If the Constitution and the laws in accordance with it are the law of the land, then acting as though one were exempt from the Constitution and laws results in acts that are against the law.
Thinking up a three syllable word for it and calling it a right doesn't change anything.
Second, it was the people declaring their independence.
None of that was of critical importance until Union troops started taking lives.
First of all, the question of whether a state or some body claiming to represent a state could secede without the consent of the union as a whole wasn't answered before the war.
Secondly, the way the process happened was highly questionable. A lot of Americans questioned whether it really was the "will of the people" or something forced on them by a determined minority.
Third, unilateral declarations of independence usually do result in war or close calls with war. The secessionists of the 1860s were more than willing to go to war. If you respect them, recognize that and don't treat them like victims.
Your point is not founded either in fact or law, therefore your contention about applicable law is false on its face.
And with regard to your contention that unilateral approval was “not answered before the war” is laughable. The country was governed by law, not popular approval.
And next, of course, you know that every seceded state took the issue to their people, but you would still try to misrepresent the issue.
And finally you attempt to roll out multiple red herrings about secession, war, and respect. Why bother?