After all of the fighting and dying and "reconstructing", the US Constitution is STILL silent on the subject. The Yankees couldn't even get that right. EVERYONE then and now knows that an amendment like that would be DOA, well except you.
"Articles of Confederation and perpetual Union between the states...”
"Every State shall abide by the determination of the United States in Congress assembled, on all questions which by this confederation are submitted to them. And the Articles of this Confederation shall be inviolably observed by every State, and the Union shall be perpetual; nor shall any alteration at any time hereafter be made in any of them; unless such alteration be agreed to in a Congress of the United States, and be afterwards confirmed by the legislatures of every State.”