The case of Dred Scoot v. Sanford (60 U.S. 393, 1856) was meant to be a federal question case. However, it became a diversity of citizenship case when Dred Scott's citizenship was challenged. The Supreme Court determined in this case that Dred Scott was a citizen of a State, under the constitution of an individual State, and because of this lacked legal standing to pursue a cause of action in a federal court.

A citizen of a State, under the Constitution of the United States of America, at Article IV, Section 2, Clause 1, can, however, pursue a cause of action in a federal court. Legal authority quoted, cited and linked.