“Secession is not a valid Constitutional concept.”
Why not? States are sovereign. They have every right to decide to join or to leave. If you do not understand the term ‘sovereign’ then maybe that is why you think as you do.
The Constitution is the supreme law of the land and it provides for a republic of divided sovereignty. The states do not own absolute sovereignty any more than the general government does. "We the People" are sovereign under God. Some of the greatest governmental usurpations and oppressions in our history have marched under the banner of state sovereignty.