Strawbridge v. Curtiss 7 U.S. 267, 2 L. Ed. 435 (1806) Strawbridge, who was a citizen of Massachusetts, sued Curtiss (who was a citizen of Vermont), and other few other people who were citizens of Massachusetts. Strawbridge sued in Federal Court based on diversity of citizenship. The Federal Trial Court dismissed the case based on lack of subject matter jurisdiction. Strawbridge appealed. Strawbridge argued that he was a citizen of Massachusetts and Curtiss was a citizen of Vermont. Therefore there was diversity of citizenship. Curtiss argued that the plaintiff and some of the defendants were all citizens of Massachusetts, therefore there was not diversity of citizenship. The Federal Appellate Court affirmed. The Appellate Court found that you need complete diversity in order to have subject matter jurisdiction. Even one defendant who is from the same State as the plaintiff, destroys diversity. Basically, since Strawbridge was a resident of Massachusetts, if any of the defendants were residents of Massachusetts, then there isn't complete diversity and the suit cannot be brought to Federal court under the theory of diversity jurisdiction. Federal courts are courts of limited jurisdiction. That means they can't hear any case, they can only hear cases brought because there is a federal law at issue (federal question jurisdiction) or there is diversity of citizenship. See 28 U.S.C. 1332. The concept of complete diversity is a construction of an act of Congres, not part of the Constitution. The Constitution only requires minimal diversity. Congress has enacted a few Statutes that establish times when you don't need complete diversity to sue in a Federal Court. (Certain types of class action lawsuits for example).