In what is understood as one of the worst decisions the Supreme Court ever made, in Dred Scott, the court determined three things: first, that living in a free state did not make a slave free, second, that a slave could not be a national citizen of the United States—a freed slave could, however, be the citizen of a particular state—and that the Missouri Compromise was unconstitutional.
This decision further polarized an already deeply divided nation. Slave owning white southerners were pleased, but abolitionists and many northerners were outraged, not only at the decision, but at what seemed like judicial overreach. Maine passed legislation, for example, providing former slaves with state citizenship while Ohio passed laws saying any slave living in the state was freed: the backlash, in other words, was intense.
The decision was reached in 1857. Four years later, the country was embroiled in the Civil War. The decision solved nothing but instead increased tensions and led both sides to dig in all the harder until a war ensued.