"At their discretion" is a more modern term, the term of art our Founders used is "at pleasure", which we still sometimes hear today in, for example, "the FBI director serves at the pleasure of the President who may fire him at pleasure, meaning for any reason whatever, or indeed for no reason."
That term "at pleasure" was never applied by any Founder to the subject of unilateral disunion.
Instead, to justify unilateral disunion they used "necessity", "necessary" conditions as defined in their own Declaration of Independence.
Of course, at pleasure secession was still acceptable to the Founders, just as in 1788, but only if by mutual consent.
To repeat: for unilateral secession our Founders believed you needed serious material breeches of contract such as they experienced and listed in the 1776 Declaration of Independence.
For at pleasure secession you need mutual consent such as they had in "seceding" from the old Articles of Confederation in 1788.
In 1860 secessionists had neither mutual consent for at pleasure disunion nor material breeches of compact to justify secession from necessity.
So they declared secession at pleasure, something no Founder ever proposed or supported.
“So they declared secession at pleasure, something no Founder ever proposed or supported.”
Tell that to the person who changed my argument regarding “states” to one involving the Founders.
“In 1860 secessionists had neither mutual consent for at pleasure disunion nor material breeches of compact to justify secession from necessity.”
Historical perspective? Not on your side of the argument.
http://bonniebluepublishing.com/The%20Right%20of%20Secession.htm