The doctrine of precedent, often expressed by the Latin maxim stare decisis ("to stand by things decided"), requires courts to decide like cases alike by following the reasoning of prior judicial decisions. It is a cornerstone of common law systems such as those of the United Kingdom, the United States, Canada, Australia, and India, though it operates more loosely in civil law jurisdictions.
Two forms are typically distinguished:
- Vertical precedent (binding): Lower courts must follow decisions of higher courts within the same jurisdiction. For example, U.S. district courts are bound by their circuit court of appeals, and all federal courts are bound by the Supreme Court.
- Horizontal precedent (generally persuasive or self-binding): A court's prior decisions guide its own future rulings. The UK House of Lords historically considered itself strictly bound by its own decisions until the Practice Statement of 1966, which allowed departure when "right to do so."
Central to the doctrine is the distinction between ratio decidendi — the legal reasoning essential to the outcome, which binds — and obiter dicta, observations not strictly necessary to the decision, which are merely persuasive. Courts may also distinguish a precedent on its facts, or in rare cases overrule it, as the U.S. Supreme Court did in Brown v. Board of Education (1954), departing from Plessy v. Ferguson (1896).
In international law, formal precedent is weaker. Article 59 of the Statute of the International Court of Justice expressly states that ICJ decisions have "no binding force except between the parties and in respect of that particular case." Nonetheless, international tribunals routinely cite prior rulings, and bodies like the WTO Appellate Body and the European Court of Human Rights treat their own jurisprudence as highly persuasive.
For MUN delegates and researchers, precedent matters when arguing that a state practice, treaty interpretation, or Security Council action establishes a pattern others should follow — even where no strict legal obligation to do so exists.
Example
In *Obergefell v. Hodges* (2015), the U.S. Supreme Court relied on precedents including *Loving v. Virginia* (1967) to extend the fundamental right to marry to same-sex couples nationwide.
Frequently asked questions
Not formally. Article 59 of the ICJ Statute limits the binding force of decisions to the parties in a given case, though international courts often cite their prior rulings as persuasive authority.
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