He misstated the intent of the Founders, and their respect for the Natural Laws of Nature's Creator. As those Founders summarized those intents applicable in this case,
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable RightsIt was in his power to set Justice aright for Dred Scott and his family. Taney refused.
The lawmaking power does NOT include the power to take away "unalienable Rights". The government and the courts exist for what purpose? According to the Founders:
... to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governedBut what happens when the government makes laws or enforces the laws in ways that impair or remove the natural rights of men? The Founders spoke to dealing with that circumstance too:
-- whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish itThat is a court, judge or jury, acting in their role as agents of the people do have the right to alter severe injustice. That is especially so in the Supreme Court.
Remember that the courts, judge or jury, and officials whose role is to investigate and possibly bring charges against defendants, also have the role of interpose between sometimes harsh and unyielding interpretation of statute law.
At the time of the Dred Scott decision, slaves were considered property and treated as such. The 14th amendment, not any court, made them citizens of the United States.