The Constitution is still silent on state secession.
The Constitution is good in many ways, but it really should have had an “escape clause” or else a flat statement that no state can ever leave. Either way. The Founders gave us a way to Amend the articles but no way to reduce the membership in the union. To me, that was a major mistake.
I guess, since the Constitution is silent on the subject, the Supreme Court decision on the secession of Texas is the final word on the issue. At least for the time being.