How could South Carolina legitimately (or with a straight face) claim a refusal (by northern states) to extradite with reference to Brown’s sons? That doesn’t make sense. It would be akin tot eh state of Washington involving itself in the George Zimmerman case. I’m not disputing your suggestion but I wonder if there could be any other case they could have referred to?
Or if it was just a smokescreen.
Not from what I can find. The whole relevant line reads, "the States of Ohio and Iowa have refused to surrender to justice fugitives charged with murder, and with inciting servile insurrection in the State of Virginia."