[P_A_I]

Yes, it was, and we had to correct that flaw in our principles at considerable expense..

-- Which proved that exceptions to the rule of law, and to Constitutional principles, do not work.

[jackbob]

Which proved that exceptions to the rule of law, and to Constitutional principles, do not work.

Two verbs in same sentence (not a criticism - I often do it). But your meaning is unclear as to what you meant by "do not work." Please explain.

[secretagent]

"Was slavery constitutional at one time?"

Yes, it was, and we had to correct that flaw in our principles at considerable expense..

Did Americans who aided slaves in escaping to Canada violate the Constitution?