The interesting thing about Dred Scott in this connection is that it was not a unanimous decision: the Court was divided 6-3.

The racism of the Court (which probably was unanimous) plus the political commitment of the majority of the justices to slavery unquestionably influenced the decision.

However: Justice Taney's reasoning from the U.S. Constitution, while self-serving, was also punctiliously correct: a case of the letter of the law trampling on its spirit.

How is this possible? Because the U.S. Constitution neither sanctioned nor forbade slavery, which was considered a social rather than a political institution. Since legally obtained slaves were commonly recognized as personal "property" like any other, the Constitution had no jurisdiction over how that personal "property" was to be "disposed of."

The point is that it took a Civil War, two Constitutional Amendments (each ratified by 2/3 of the states) and a century (and more) of changing attitudes to rectify the situation.

No quick fix, Brits.