I’m not a Constitutional Scholar, but when I was in school, I was taught that both California and Texas had the right to secede from the union. This right was incorporated into the treaty between the California Republic and the US when California joined the union. Texas is in a similar situation as the only other nation to voluntarily join the US.
That being said, I think it would be a stupid idea.
For that to be true would mean that those states have a right denied to every other state - a situation that nothing in the Constitution supports. It also ignores the fact that both Vermont and Hawaii were also nations before they became states.
I think an equally relevant question is “can states AFFORD to secede”?
In the case of California, where I live, CA would sink to the bottom of the Pacific Ocean if it split, financially speaking.
I don't think California has that right, however, if you put it to a vote, most Americans would vote San Francisco and Los Angeles out of the union. *gri*