Proof please. You don’t get to claim a thing without proof. We can easily prove that the import of slaves continued through the north after 1807, but can you prove the same about the South, especially after the CW began?
From 1808 until the Civil War, most historians estimate about 10,000 slaves per year were illegally imported into the US. It wasn't until the Lincoln administration that the laws against slave importation were seriously enforced -- they actually hung a captain of a slave ship as the 1819 law authorized. Before that, they would occasionally capture and seize a slave ship and fine the owners, but that was all that would happen. It was a small price to pay considering the amount they could make every time they got a load of slaves ashore.
You can? What Northern state imported foreign slaves then?