The U.S. Constitution is notable for both its adaptability and its durability. Over the course of its existence, the Constitution has accommodated and invalidated slavery, survived disunion and civil war, allowed and prohibited racial segregation, specified freedoms and rights that government may not abridge and been a departure point for identifying liberties not itemized by the document itself. Although time has passed, circumstances have changed and understanding has evolved since its ratification, the Constitution in form remains unaltered except for twenty-six amendments to it since 1791. Appearances are deceiving, however, to the extent that limited textual revision might suggest minimal development or even consistency of principle and understanding. As evidenced by volumes of case law that have accumulated over two centuries, including more than five hundred compiled by the U.S. Supreme Court, the Constitution itself has been a source of controversy and debate from which doctrine and principle have evolved. Because it is not always self-defining, especially with respect to its most profound but broadly stated passages, the Constitution challenges and effectively requires each generation to contribute to its development and consequent meaning.
The judiciary's primacy in construing the Constitution, and consequent power to define and gloss its meaning, was established in 1803. Chief Justice Marshall, in Marbury v. Madison, determined that it was the Court's power "to say what the law is." Few decisions in constitutional history rival