“That last one would have been a critically nasty bone of contention in congressional negotiations. The Southern attitude would have been that slaves are property, property is sacred, and thus runaway property should have no protection simply because it crosses a new international boundary. “
Is there historical evidence of this or is it an educated guess? I don’t see how this would have been any different than the situation that already existed between the US and Canada. Canada didn’t honor the American runaway slave law and there would be no reason for the US to do so either.
Either way the runaway slave issue is particularly interesting if secession had gone forward.
Had Lincoln let the initial seven states go the balance of power in the US Congress shifts dramatically bringing an end to laws favoring slavery. The border states would have needed to be brought along, but slavery was not embedded in their economy like it was in the cotton belt. Compensated emancipation like the British used would have worked.
The end of the runaway slave law would have posed a major problem for the rump seven state CSA. While getting to Canada was difficult crossing into the American border states was not much of a problem.
It’s an educated guess on the part of two historians: Shelby Foote and Forrest McDonald.