[FLT-bird]

Well put. In the North, public sentiment strongly favored fugitive slaves, even to the point of crowds gathering to impede the efforts of slave catchers. Alert Southern slaveholders realized well enough that effective enforcement of fugitive slave laws in the North had become impossible by the time of Lincoln’s election.

Had they? I'd have to see some evidence of that. Lincoln promised strengthened fugitive slave laws.

Of course we know slavery was safe within the union. Nobody thought the federal government had the power to ban it and there were enough slaveholding states to prevent the passage of any constitutional amendment that would have banned it. There was a fugitive slave clause in the Constitution that protected slave owners. For any state that seceded however - assuming it be allowed to depart in peace - slavery was doomed and quickly. The US would immediately be a foreign country with no obligation to return their escaped slaves.

[Rockingham]

Several Northern states passed laws that forbade local authorities from helping apprehend fugitive slaves. In addition, the Northern public often actively helped fugitive slaves. The net result was that Southern slaveholders frequently complained about the lack of enforcement of the Fugitive Slave Act.

Absent the restraints of Northern public opinion, slaveholders expected that the Confederacy as a whole would be more diligent and effective in controlling their slave population and preventing them from fleeing captivity.