The evidence is really self-evident - if these signing statements had any force of law they would have availed themselves of it. None of the rebelling states pointed to these statements and declared this so-called right. None.
And that is because even the slavers knew that there is no “right of secession” - especially not a unilateral right. The only way out of the union is through mutual accord of ALL the states or by revolution and the force of arms.
False. They asserted their right to secede under the 9th and 10th amendments. Since nowhere in the constitution is it forbidden and since the argument cannot be made that the bill of rights already contains all rights the states have, the states clearly do have the right to unilaterally secede. The express reservations of multiple states are prima facia evidence of the original intent of the ratifying bodies of sovereign states.