Fun facts
Virginia, Rhode Island, and New York included so called Resumption Clauses in their ratification of the Constitution, stating their right to leave the Union if they felt the government was oppressive.
The Constitution implicitly has a co-equality clause, meaning that all states have equal rights.
The 10th Amendment specifies that any power not delegated to the federal government by the states, and not denied the states by the Constitution, is a right of the states.
The Constitution does not address secession, denying the federal government authority to address it and guaranteeing it to the states.
President James Buchanan did not try to stop the Southern states from seceding because he recognized that the federal government did not have the right to intervene.