To quote Lysander Spooner:
“If it really be established, the number of slaves, instead of having been diminished by the war, has been greatly increased; for a man, thus subjected to a government that he does not want, is a slave. And there is no difference, in principle—but only in degree—between political and chattel slavery.”
Every natural right not expressly given up, or, from the nature of a social compact, necessarily ceded, remains.” Samuel Adams
On that note: The power to prevent secession was voted down. During the Federal Convention and 1861 (see below ).
28 nays to 18 yeas
"Under this Constitution, as originally adopted and as it now exists, no State has power to withdraw from the jurisdiction of the United States; and this Constitution, and all laws passed in pursuance of its delegated powers, are the supreme late of the land, anything contained in any constitution, ordinance, or act of any State to the contrary notwithstanding."
http://memory.loc.gov/cgi-bin/ampage?collId=llsj&fileName=052/llsj052.db&recNum=378&itemLink=D?hlaw:3:./temp/~ammem_iHF8::%230520379&linkText=1
Your argument is essentially this: The south had a “natural right” to secede in order to perpetuate and extend the institution of chattel slavery. The suggestion that a group of people have the “natural right” to deny the natural rights of others is absurd.
No founder, nor any natural rights theorist; not Socrates, Plato, Aristotle, Aquinas, Bacon, Blackstone, or Locke ever argued for an unqualified, unlimited right to political seperation. What you describe as a “Natural Right” is simply anarchy or tyranny.