By exercising its power to determine whether federal and state government actions are constitutional, the Supreme Court has developed a large body of judicial decisions, or "precedents," interpreting the Constitution. Rules and principles established in prior cases inform the Court's future decisions. The role that precedent plays in the Court's decisions on highly controversial issues has prompted debate over whether the Court should follow or overrule rules it established in prior decisions. Such questions underscore the challenges the Court faces in maintaining stability in the law by adhering to precedent under the doctrine of stare decisis so that parties may rely upon its decisions, while at the same time correcting prior decisions that rest on faulty reasoning, unworkable standards, abandoned legal doctrines, or outdated factual assumptions. One notable example of a precedent that has prompted significant debate is the Supreme Court's 1992 decision in Planned Parenthood v. Casey . In Casey, a plurality of Justices reaffirmed the core aspects of the Court's earlier holding in Roe v. Wade that a woman has a protected constitutional liberty interest in terminating her pregnancy prior to fetal viability, stating that the essential holding of Roe "should be retained." But the plurality's opinion in Casey suggests that several Justices who voted to reaffirm Roe had significant doubts about the quality of its reasoning. Despite these doubts, the Casey plurality decided that other considerations required reaffirming Roe 's central holding, including societal reliance on a fundamental constitutional right; concern for the Court's legitimacy as an institution; and the principle that the Court should adhere to rules in its prior decisions (i.e., stare decisis), particularly when a case implicates a highly divisive issue like abortion. Although the Supreme Court's decision to retain a precedent may prompt significant debate, the Court's overruling of precedent can also be controversial, as the Court's 2010 decision in the campaign finance regulation case Citizens United v. FEC illustrated. That case established that the First Amendment prohibits governments from restricting independent expenditures on political speech related to an election campaign by corporations, labor unions, and other organizations. In reaching this result, the Court overturned its decision in Austin v. Michigan State Chamber of Commerce , which had held that the government could prohibit political speech funded from a corporation's general treasury fund based on the fact that the speaker was a corporation. The Court's overruling of Austin in Citizens United sparked debate about whether the Court should have adhered more strictly to the principle of stare decisis. Debate over the role that stare decisis plays in the Supreme Court's decision making continued during the 2017-2018 term as the Justices overruled four longstanding precedents. For example, in Janus v. American Federation of State, County, and Municipal Employees, the Court overturned its 1977 holding in Abood v. Detroit Board of Education and determined that laws that require public employees to pay "fair share" fees to the union designated to represent their bargaining unit, even if the employees are not members of the union, violated the First Amendment by compelling speech on matters of public concern. And in South Dakota v. Wayfair , the Court overturned holdings in two earlier cases, concluding that the Commerce Clause does not restrict states from requiring retailers that lack a physical presence in the state to collect and remit taxes on sales made to state residents. In light of these developments, this report examines how the Supreme Court determines whether to overrule its prior decisions on questions of constitutional law. It provides an overview of the doctrine of stare decisis, under which a court generally follows rules adopted in prior decisions in future cases with arguably similar facts. It discusses how Justices who have adopted textualism and originalism as philosophies for interpreting the Constitution handle conflicts between precedent and their judicial philosophies. Finally, the report examines various factors that the Court weighs when determining whether to overrule or limit its precedents interpreting the Constitution, providing examples from the Court's recent jurisprudence. Understanding stare decisis may assist the Senate in evaluating the judicial philosophy of nominees to the federal courts. For example, in July 2018, President Donald J. Trump announced the nomination of Judge Brett M. Kavanaugh of the U.S. Court of Appeals for the District of Columbia Circuit to fill retiring Justice Anthony M. Kennedy's seat on the Supreme Court of the United States. Members of Congress, the public, and legal scholars expressed interest in Judge Kavanaugh's views on stare decisis, as they could potentially provide insight into his future decisions in important areas of constitutional law, including abortion, affirmative action, labor law, and separation of powers, among others. The Appendix to this report lists Supreme Court decisions on constitutional law questions that the Court has overruled specifically during its more than 225-year history. Stare decisis , which is Latin for "to stand by things decided," is a judicial doctrine under which a court follows the principles, rules, or standards of its prior decisions or decisions of higher tribunals when deciding a case with arguably similar facts. The doctrine of stare decisis has "horizontal" and "vertical" aspects. A court adhering to the principle of horizontal stare decisis will follow its prior decisions absent exceptional circumstances (e.g., the Supreme Court following its decisions unless they have become too difficult for lower courts to apply). By contrast, vertical stare decisis binds lower courts to follow strictly the decisions of higher courts within the same jurisdiction (e.g., a federal court of appeals must follow the decisions of the U.S. Supreme Court, the federal court of last resort). This report addresses how the U.S. Supreme Court determines whether to overrule its prior decisions. Thus, this report discusses only horizontal stare decisis. The Supreme Court applies the doctrine of stare decisis by following the rules of its prior decisions unless there is a "special justification"—or, at least, "strong grounds"—to overrule precedent. In adopting this approach, the Court has rejected a more formalistic view of stare decisis that would require it to adhere to its prior decisions regardless of the merits of those decisions or the practical implications of retaining or discarding precedent. Instead, while the Court has stated that its precedents are entitled to respect and deference, the Court considers the principle of stare decisis to be a discretionary "principle of policy" to be weighed and balanced along with its views about the merits of the prior decision and several pragmatic considerations when determining whether to retain precedent in interpreting the Constitution or deciding whether to hear a case. The Court may avoid having to decide whether to overrule precedent if it can distinguish the law or facts of a prior decision from the case before it or, rather, limit the prior decision's holding so that it is inapplicable to the instant case. The doctrine of stare decisis in American jurisprudence has its roots in 18 th century English common law. In 1765, the English jurist William Blackstone described the doctrine of English common law precedent as establishing a strong presumption that judges would "abide by former precedents, where the same points come again in litigation" unless such precedents were "flatly absurd or unjust" in order to promote stability in the law. And the Framers of the U.S. Constitution, who conferred the "judicial power" of the United States on the Supreme Court and lower federal courts, echoed Blackstone in their writings during the late 18 th century, favoring judges' adherence to judicial precedent because it limited judges' discretion to interpret ambiguously worded provisions of written law. For example, writing in the Federalist during the debates over adoption of the Constitution at the end of the 18 th century in an essay addressing concerns about judicial power, Alexander Hamilton argued that courts should apply precedent to prevent judges from having unbounded discretion to interpret ambiguous legal texts. However, historical sources provide only limited insight into the Founders' views on stare decisis, and it is unclear whether Hamilton was referring to the presumption that a court should adhere to its own prior decisions or, rather, those of higher tribunals. Despite the Founders' general approval of judges following precedent, at least one Framer, James Madison, acknowledged that courts should occasionally make exceptions to the doctrine of stare decisis for certain policy reasons. During the tenure of Chief Justice John Marshall in the early 1800s, the Supreme Court combined a strong preference for adhering to precedent with a "limited notion of error correction" when precedents had been eroded by subsequent decisions, were "premised on an incomplete factual record," or were clearly in error. Another characteristic of these early decisions is that the Court was reluctant to overrule prior decisions when doing so would upset commercial reliance interests (e.g., precedents concerning matters of property or contract law). Although the Court has only recently sought to enumerate the factors it considers when determining whether to overrule precedent, the Court has long sought to strike a balance between maintaining a stable body of consistent jurisprudence while at the same time preserving some "mechanism for error correction." The Supreme Court has often stated that following its prior decisions supports the legitimacy of the judicial process and fosters the rule of law by encouraging stability, certainty, predictability, consistency and uniformity in the application of the law to cases and litigants. As Justice Lewis Powell once remarked, "the elimination of constitutional stare decisis would represent an explicit endorsement of the idea that the Constitution is nothing more than what five Justices say it is." Thus, one view is that following the carefully considered decisions of past Justices by adhering to principles of stare decisis supports the Court's role as a careful, unbiased, and predictable decisionmaker that decides cases according to the law rather than the Justices' individual policy preferences. Another reason for adhering to stare decisis is to save judges and litigants time by reducing the number and scope of legal questions that the court must resolve in litigation (e.g., whether the Court may declare a federal law unconstitutional—a question settled in the 1803 decision of Marbury v. Madison ).