He wrote one of the worst decisions in the history of the Supreme Court.
The concept that people can be property wasn't ended in the US until the 13th amendment passed after the Civil War.
Dred Scott said you couldn't take property into another state and say it isn't property anymore. For example, you can't steal an F-150 in Tennessee and drive it to Vermont and say it's yours. Pretty cut and dried.
The Supreme Court decided to leave the issue of slavery to Congress (which kept punting) and merely interpreted existing law.
How radical.
But a correct application of the existing constitutional law for that time period.