These states acted as independent sovereigns when they negotiated the Articles of Confederation, Constitution and supported the Declaration of Independence. They wrote those resevations of their right to withdraw at the time of their ratifications. Secession is not covered in the Constitution, but in the same manner the States were created, the justification for secession comes from the claims of the secessionists and the agreements arrived at from the eventual resolution of the matter with opposing parties.
Historically justifications in this sort of matter were validated, or not, by open warfare. Constitutions are contracts. When disputes arise that involve irreconcilable differences, the party most adept at exerting their will wins and awards itself the title of right in whatever justifications it expounds.
Can you post that? And can you also post where the US Congress which received the ratifications left any record of whether or not they considered such resolutions?