American law is based on the principle of precedent, meaning that if a court has already ruled on a given legal issue and another case arises with the same legal issue, the holding in the previous case will be applied to the new case. The use of precedents helps to promote stability in the legal system, as all parties are given notice as to the current state of the law. Adhering to the use of precedent is also known as the doctrine of stare decisis (Latin: "it stands decided").
Precedents also have a role to play when new legal issues are presented to courts. Parties for both sides of a case look to cases that have been decided in the past that bolster their current arguments. When deciding new legal issues, sometimes courts expand previous precedents. Sometimes they distinguish the case at hand from the established precedent by pointing out how the previous ruling is not applicable to the facts of the new case.
Although rare, sometimes courts overrule a precedent. Even if a lower court disagrees with a precedent established by a higher court, the lower court remains bound by that precedent until it is overruled by the higher court. For instance, a U.S. District Court cannot overrule a decision of the U.S. Supreme Court, but the U.S. Supreme Court may make a decision that, in effect, overrules itself. Courts within a given District and Circuit are bound by precedents within their own Districts and Circuits, respectively. However, they are not necessarily bound by precedents in other Districts and Circuits. Only U.S. Supreme Court precedents are binding on all courts. Often, the U.S. Supreme Court decides to hear a case because different U.S. Courts of Appeals have come to different conclusions on the same legal issue. The Supreme Court may decide such cases in order to harmonize the law. The following examples illustrate precedents in the federal court system.
Example: Tinker v. Des Moines, 393 U.S. 503 (1969)
In Tinker v. Des Moines, the Supreme Court ruled that students had a First Amendment right to wear black armbands to school to protest the Vietnam War. Students in subsequent cases have tried to use Tinker to argue that various school regulations violated their First Amendment rights.
In Hazelwood School District v. Kuhlmeier, 484 U.S. 260 (1988), the Supreme Court held that high school administrators have the authority to censor articles in a student newspaper. The Court distinguished this case from Tinker, saying that the administrator's actions did not violate the free speech rights of students because the school: 1) ultimately retained administrative authority over the paper; 2) it had to look out for the privacy rights of other students (which may have been compromised by certain articles in the paper); and 3) the articles in the paper could be seen as carrying the imprimatur of the school, i.e., readers might mistake the articles as the views of the school, and not those of the student journalists.
In Morse v. Frederick , 551 U.S. ___ (2007), the Supreme Court held that students do not have a right to promote speech (specifically, a banner reading "Bong Hits for Jesus") at a school event that could be interpreted as advocating the use of illegal drugs. The Court distinguished this case from Tinker saying that Tinker's speech was political and did not disrupt the learning environment. However, due to the adverse consequences of illegal drug use, the principal had a compelling interest in preventing this type of speech.
Thus, Tinker stands for the proposition that students have the right to express themselves in school so long as their conduct does not impinge on the rights of others. However, Hazelwood and Morse are distinguished from Tinker, holding that this right is not absolute and does not extend to school newspapers or to speech promoting illegal drug use.