Final answer:
Dred Scott argued for his freedom based on his residence in free territories, but the Supreme Court denied his claim stating that Black individuals could not sue in federal court and were not U.S. citizens. The ruling also invalidated the Missouri Compromise, endorsing slavery's expansion into the territories.
Step-by-step explanation:
Legal Basis for Dred Scott's Claim
Dred Scott based his legal argument for freedom on his prolonged residence in free territories. Scott, an enslaved African American, contended that by living in Illinois and the Wisconsin Territory, areas where slavery was prohibited, his status shifted from enslaved to free. These regions were originally part of the Northwest Territory in which the 1787 Northwest Ordinance had banned slavery. Upon returning to Missouri, a slave state, he initiated legal action after his bid for freedom was denied by his owner.
However, when reaching the Supreme Court in Dred Scott v. Sandford, the justices deemed that Scott had no legal right to sue for his freedom in federal court. Chief Justice Roger Taney penned the majority opinion and declared that Black people, whether enslaved or free, were not considered U.S. citizens and thus could not sue in federal courts. Taney took a step further to declare the Missouri Compromise unconstitutional, asserting that Congress did not possess the authority to prohibit slavery in the territories, reinforcing the notion that slaves were regarded as private property.
The Supreme Court ruling was a significant pro-slavery decision, which heightened tensions leading up to the American Civil War and has since been infamous for its denial of Black citizenship rights and support for the expansion of slavery into western territories.