Well, yes, it would have. If all current slaves were freed, and it’s an illegal act to import any new slaves, anyone who tried to own slaves could be sent to prison for the act.
My point was that that little law in the US Constitution would not have deterred a people who were set on slavery to the point of seceding from the US and forsaking that very same Constitution.
A group of people who so objected to the Constitution that they wanted to return to the Articles of Confederation, would have, had the North bought all slaves, simply bought more slaves. If the North tried to impose the law on them, they would have seceded and said they no longer abided by the USC.