The reverse is also true. If there had been a line item in the Constitution declaring that slavery was legal, the Northern states would not have ratified the Constitution. Hence no United States. The restriction of slavery to the South was a direct result of the Dred Scott decision by the Supreme Court in 1857. Prior to that court case, the efforts of the abolitionist movement was to get the U.S. Government to outlaw slavery. After Dred Scott, they realized that there was no legal route for the Federal Government to end slavery in the States where it was legal. The abolitionists changed their efforts to preventing the introduction of slavery into the territories of the U.S.
Dred Scott did more than that.
It effectively declared abolition unconstitutional, even in Northern states.
First it said that property (a slave) was always property, regardless of which state it was taken to.
So slave-holders could take hundreds of slaves to any northern state, and keep them there as slaves.
Then Dred Scott said, Africans could never be freed citizens with normal rights, such as voting and serving on juries.
This was much further in the direction of pro-slavery than our Founders were willing to go in 1786, and it provoked a Northern backlash against slavery, fueling the new Republican party's popularity.