Luke, despite my large disagreement with you, I found what you just posted to be interesting.
What if a state, like Texas for example, seceded and retained the United States Constitution as its governing document. Say this "United States of Texas" seceded and kept the Constitution but formed a new Supreme Court, Senate, and House of Representatives, how would you feel about that? Say they did all that and offered a free trade and mutual defense alliance with the US government?
Oh, this was an interesting question that I was planning on answering before, but forgot.
Anyways....
In your example, Texas secedes from the US, but keeps the Constitution. Umm, there's no way to do that. Seceding, by definition, means removing yourself from the authority of the Constitution. There's no way to remove yourself from the authority of the Constitution and keep the authority of the Constitution at the same time. That's logically impossible. I think what you mean is what if Texas created a
new document which is
nearly identical to the Constitution, and then seceded, and governed itself by that. Well that's a different document, then, not the Constitution.
So it's still treason for Texas or any other state or group of states to secede under any circumstances, with one exception: If 3/4 of the states come together to create a convention, as outlined in the Constitution, and they throw out the Constitution and dissolve the Union, then that is legal. Or if 2/3 of the Senate and the House of Representatives create an amendment to the Constitution nullifying the rest of the Constitution and dissolving the Union, and it is ratified by 3/4 of the state legislatures, then that is legal. Any other method of secession or dissolving any part of the Union is treason.