That should have been hashed out 70 years earlier. They Northern states agreed to it back in 1789 when they ratified the Constitution. When the country was young, facing imminent threat of invasion and war with England and needed the agricultural products the South was able to produce with slave labor, it was OK.
At the time of the Constitution, slavery had been effectively eliminated in only one state, MA. Even there it wasn’t formally and legally ended till 1865 by 13A.
In 1789, slavery was believed by everyone, including the slave owners, to be on its way out. It wasn’t very profitable and it was expected the institution would die a natural death. Not surprisingly, few saw a need to create immense uproar over an issue that would go away by itself.
It wasn’t until the early decades of the 19th century, when slavery started to become wildly profitable, that it became increasingly an issue. It’s one thing to put up with a fading evil. It’s quite another to put up with one whose proponents insist it must be allowed to spread in both time and space.
Does your comment mean that if slavery wasn’t prohibited by the Constitution nobody thereafter had any right to work against it?
In 1860 almost all northerners, and all northern politicians, agreed that the Union had no right to interfere in slavery within a state. To be fair, a good many of the pols were probably lying, much like Obama claiming to be against gay marriage as recently as two years ago.