One problem Walt, is that Lincoln is not stating that seccsion is illegal, he's stating that it would be illegal to leave without settling the bill. And a delegation was sent to Washington to meet with him to discuss this, aided by the efforts of US Supreme Court Justice Campbell. The south was more than willing to repay any debts, Licoln was unwilling to allow the golden goose to leave.
Nonsense, according to the resolution they were to 'negotiate friendly relations' between two governments and discuss 'all questions of disagreement between the two governments.' That would have required Lincoln to recognize the southern rebellion as legal and to treat with the Davis regime as if it were a soverign government. That killed the scheme right off the bat.
And therein lies the rub. And therein lies the case of States Rights vs. Federal rights. It is indeed about money and who has the loudest voice in Washington.
Would that we could have resolved the issue way back then; but alas, after much blood and suffering, the issue is still alive and undergoing a new awakening.