BENEATH THE SURFACE of nearly all discussions of civil liberties, there lies a silent partner—the notion that individuals are entitled to a measure of autonomy and noninterference from both the government and from the world around them. Freedom of expression, freedom of the press, freedom of religion: These are all about the right to say to the government, "Let me be."

This right to be left alone, however, is not only a component of the written liberties guaranteed by the Bill of Rights. It has also become accepted as a constitutional guarantee in its own right—the "right to privacy." Over the years, the U.S. Supreme Court has ruled that the right to privacy includes both the right to make certain fundamental decisions (relating in particular to family matters) without governmental interference and to avoid forced...