" The price of slaves grew so high that a sizable number of white southerners urged the reopening of the African slave trade. In the 1850s, legislatures in several states, including South Carolina, proposed reopening the trade. Adopting this measure would have violated federal law. Some “reopeners” believed that the federal ban on the trade was unconstitutional; others were keen to nullify it, in a dress rehearsal for secession. "

― Jill Lepore , These Truths: A History of the United States