John: You've given the "textbook" answer stating only the SC can overturn an earlier SC decision, or having  a Constitutional Amendment. However, it doesn't work like that in real life. Here are three examples: In 1982 Congress amended the Voting Rights Act of 1965 to overrule Mobile v. Bolden; in 1988 it overruled Grove City College v. Bell by passing the Civil Rights Restoration Act, which broadened coverage of Title VI of Civil Rights Act of 1965, and in 1991 Congress passed another Civil Rights Act that specifically reversed no fewer than five SC cases. (Source: The American Prospect, Dec. 19, 2001, article by Leon Friedman).