The final nail in the Missouri Compromise's coffin, this Supreme Court Case struck down the Compromise as unconstitutional based on the grounds that any "negro, whose ancestors were imported into [the U.S.], and sold as slaves" was not a citizen and therefore not subject to U.S. Federal law. (Source)

Also, the Supreme Court found that the Federal government had no say in the matter of slavery for any state or territory added after the formation of the United States in the late 18th century. The Supreme Court Chief Justice Roger B. Taney believed this would set the matter of slavery to rest…but it only raised the stakes and make abolitionist parties in the North boiling mad.