ON Dec. 15, 1791 - 200 years ago this Sunday - Virginia became the 11th state to ratify 10 amendments to the still-new Constitution of the United States. The Bill of Rights became the law of the land.A century and quarter would pass, however, before American lawyers and judges began to discover in the Bill of Rights tools to shelter individuals from the actions of government. This was the legal manifestation of a much greater moral and political development of the early 20th century - the crystallization in the minds and hearts of Americans of a vision of individual liberty, as opposed to national liberty, that before had been inchoate. Why did Americans start to view themselves not only as free citizens within a context of republican government, but also as sovereign beings deserving certain protections from even their own government? The reasons are complex, but at their heart is the rapid expansion of government power in the 20th century. Probably few Americans today could identify the specific safeguards included in the Bill of Rights. Yet for virtually all Americans the Bill of Rights is enshrined as a symbol of the principles that government must operate according to rules, that it must be fair and compassionate, and that individuals enjoy certain zones of liberty even against duly enacted expressions of the majority's will. As a living appendage to a living Constitution, the Bill of Rights will have to adapt to changing times and circumstances in its third century. Efforts will continue to find within the "emanations" of the Bill of Rights constitutional sanctuaries for privacy, including sexual and reproductive privacy. New issues regarding the relationship of church and state are looming. Will the war against drugs require more flexible search-and-seizure standards under the Fourth Amendment? Has free speech gone too far in this time of burgeoning pornography and hate speech? These issues and many others will crop up on the Supreme Court's docket in the years ahe ad. The Bill of Rights enters its third century as a secure corner stone of American liberty. But the ground will keep shifting around it. Its supporters must be vigilant.