Not legal? Rather a bold statement, I would say. Last time anyone attempted formal withdrawal from the United States, something like 125 years ago, the armaments of the United States blocked the path to independence. The Union endured. But that settled only the practical, not the theoretical, side of the question.
Enough said anyway about the Late Unpleasantness of 1861-65. What...












I am in no way a Marxist. Having been an engineer in defense for 35 years, I know the rules, and the clearances. Companies like Raytheon could decide to stay in Texas, but since they are headquarted in Massachusetts, and perform highly classified work for the US government, I don't think those plants would stay in Texas. It's not where the money would be.
Of course, they could stay, but they probably wouldn't have the billion dollar contracts from the US. If Texas became a 'nation', I don't see them awarding big contracts right away.
You should be more careful about reading the posts. I revere Madison and Adams, I'm a little more careful about Jefferson, since he was a little more 'democratic' vs. repulican.