Stare Decisis refers to the legal doctrine wherein a Judge lets a previous ruling or precedent stand.
However, Judges are not always correct and understandings regarding what is Constitutional are not always static.
The classic example of this is the notion of "separate but equal." In Plessy v. Ferguson, SCOTUS ruled that separate but equal was constitutional. Courts relied on this decision using state decisis for years until the ruling was challenged and overturned in Brown v. Board of Education wherein the ruling was overturned.
