: to stand by that which was decided
Stare decisis is a central concept of common law courts. Under the principle of stare decisis, common law courts "are slow to interfere with principles announced in the former decisions and often uphold them even though they would decide otherwise were the question a new one." (156 Pacific Reporter, second series 340, 345)
The legal philosophy governing common law courts deems it best to overturn a preexisting legal precedent only in cases where good cause is shown to favor the change.
Stare decisis is of limited application to U.S. constitutional law, since the U.S. Supreme Court is allowed great latitude both in deciding which cases to hear, and often tends to choose such cases to create precedents that it expects to have far reaching effects in courts subordinate to its authority. Still, the broad notion of stare decisis is one that Supreme Court Justices tend to grant at least some degree of respect, since to do otherwise places them at risk of being labelled "activist jurors."
For non-lawyers, Ronald Dworkin's Law's Empire provides some fascinating insights into the notion of the doctrine of precedent which has been a central (if sometimes covert) source of stress and tension in American politics, particularly citizens' irritation with and frequent misunderstanding of the workings of American courts and the judiciary branch of government.