The Dred Scott decision was not necessary to legitimize slavery.
The United States Constitution did that upon adoption. The U.S. Constitution enshrined slavery.
And it was the historical slave states that voted to make it so. Those slave states being: New York, New Jersey, New Hampshire, Connecticut, Pennsylvania, Massachusetts, Rhode Island, Delaware, and Maryland.
Virginia, North and South Carolina, and Georgia were also slave states. Never forget to cast 4/13ths responsibility in that direction.
"Enshrined" is your word, not our Founders, FRiend.
In fact, our Founders' attitude toward slavery was very different from "enshrined".
They all believed -- even Southern slaveholders like Washington, Jefferson & Madison -- that slavery was a moral wrong which should be abolished, eventually.
They also believed Congress had full authority to abolish slavery in US territories, an authority which Crazy Roger Taney singlehandedly abolished in his Dred Scott Ruling.
As you well know, Cracy Roger's ruling P.O.'d a lot of Northerners, including this one:
"To meet and overthrow the power of that dynasty, is the work now before all those who would prevent that consummation."
A.L. "House Divided" June 16, 1858
I see what you did there. But even though it was legal in all colonies, it was not equally practiced or “appreciated” everywhere.