The key issue in the Dred Scott decision of 1857 was the status of enslaved people and their rights under U.S. law. The Supreme Court ruled that Dred Scott, an enslaved African American man who had lived in free territories, could not sue for his freedom because he was not considered a citizen but rather property. This ruling extended the reach of slavery and nullified the Missouri Compromise, which had aimed to limit the expansion of slavery. The decision intensified sectional tensions between the North and South, contributing to the outbreak of the Civil War. It remains one of the most controversial decisions in U.S. Supreme Court history.