How did the supreme court uphold slavery? by denying citizenship by determining guilt by declaring slavery laws legal by defining residency

The correct answer is: By denying citizenship.

This happened in Dred Scott legal case in the Supreme Court on March 6th, 1857, it was ruled that a slave that who had resided in a free state and territory was not entitled to his freedom, in this case referring to Dred Scott. The Supreme Court stated that no African American could be a citizen of the United States. With this decision began the controversy to civil war.