In the United States, laws have a number of sources. Along with statutes and regulations, authoritative cases also create enforceable laws. According to the Cornell University Law School’s Legal Information Institute, courts often rely on precedents in making their decisions. Legal precedents are previous relevant rulings which may control later cases.

It should be noted that not all precedents are equal. United States Supreme Court rulings, for example, will be authoritative for almost all cases in the country. This is because the U.S. Supreme Court is the highest court in America. A decision in a Texas state court, however, will not be controlling in a case tried in a Nevada state court.  

Planned Parenthood of Southeastern Pennsylvania v. Casey, a U.S. Supreme Court case, explains the rationale behind the use of precedent. The case notes that if courts were required to review all legal issues that appeared in every case, judicial systems would become completely bogged down. Requiring judges to accept prior interpretations of laws allows for a more efficient adjudication of legal issues.

While there are limited situations in which prior courts’ errors must be reversed, it is a judicial necessity that the doctrine of precedent is followed. As the court notes in the Planned Parenthood case, overruling prior decisions by the Supreme Court would undermine the legal foundation of the country. The court explains that precedent is particularly important in controversial cases. This is because contentious court decisions must withstand opposition. If courts were to neglect prior decisions, the judicial system would lose its authority. In addition, the country would lose confidence in the powers of the judiciary.