What was dred scott vs sandford and why was it significant?

Dred Scott v. Sandford, 60 U.S. 393, also known simply as the Dred Scott case, was a landmark decision by the United States Supreme Court on US labor law and constitutional law. It held that "a negro, whose ancestors were imported into, and sold as slaves", whether enslaved or free, could not be an American citizen and therefore had no standing to sue in federal court, and that the federal government had no power to regulate slavery in the federal territories acquired after the creation of the United States. Dred Scott, an enslaved man of "the negro African race" who had been taken by his owners to free states and territories, attempted to sue for his freedom. In a 7–2 decision written by Chief Justice Roger B. Taney, the court denied Scott's request. The decision was only the second time that the Supreme Court had ruled an Act of Congress to be unconstitutional.