” There have to be legitimate causes for revolution. “
You haven’t yet listed these legitimate causes nor cited a source.
” There is no legal basis for secession. “
Charles Francis Adams Jr came to a different conclusion when he investigated the issue. And being a direct descendant of the two Massachusetts Presidents he was hardly influenced by a connection with the South.
I don't care what conclusion he came to, there is no legal basis for secession.
There is no provision in the Constitution for it to occur.