Why courts follow earlier decisions, how legal authority flows through the court system, and why the format of a citation matters.
When a court decides a case, its ruling does more than resolve the dispute between the parties in front of it. The court's written explanation of why it ruled the way it did — its legal reasoning — becomes part of the body of law. Future courts facing similar questions are expected to reach the same result using the same reasoning.
This is the doctrine of precedent: the principle that a court's earlier decision on a legal question should guide — and in some cases, bind — later courts facing the same question.
"The very concept of the rule of law underlying our own Constitution requires such continuity over time that a respect for precedent is, by definition, indispensable."
— Planned Parenthood v. Casey, 505 U.S. 833 (1992)A prior court decision that establishes a legal principle or rule applied to later cases with similar facts or legal questions.
A decision from a higher court in the same jurisdiction that a lower court must follow. Also called "mandatory authority."
A decision from another jurisdiction, a lower court, or a dissenting opinion that a court may consider but is not required to follow.
The specific legal rule decided in a case. Only the holding creates binding precedent — not background discussion (dicta).
Precedent isn't just an academic concept. It determines what happens in real courtrooms. If you are a self-represented litigant, a student, or a researcher trying to understand how a law applies to a specific situation, precedent is the reason you cannot simply read a statute and know the answer. Courts have interpreted those statutes in dozens of cases, and those interpretations — built up over decades — are often as important as the statutory text itself.
A citation to a case is not a formality. It is the address of a specific legal ruling in a specific printed or electronic volume. When you cite Brown v. Board of Education, 347 U.S. 483 (1954), you are telling the reader exactly where to find the Supreme Court's holding that segregated public schools are unconstitutional. Without that address, the argument has no anchor.
Stare decisis is Latin: stare decisis et non quieta movere — "to stand by decisions and not disturb settled matters." It is the formal legal doctrine that requires courts to follow their own prior decisions and the decisions of higher courts in the same system.
The doctrine has two dimensions. Vertical stare decisis means a lower court must follow the decisions of higher courts above it in the same system. Horizontal stare decisis means a court generally follows its own prior decisions, though it retains some power to overrule itself when the prior decision was clearly wrong or conditions have fundamentally changed.
A U.S. District Court must follow decisions of the Court of Appeals for its circuit, and both must follow the U.S. Supreme Court. No exceptions. This is the strict, mandatory form of the doctrine.
The Supreme Court generally follows its own past decisions, but it can overrule them. Brown v. Board overruled Plessy v. Ferguson (1896). Courts apply a strong presumption in favor of stability before overruling.
Departing from precedent requires more than a new court disagreeing with an old one. Courts use several tools to narrow or avoid a precedent without formally overruling it:
Distinguishing: The court finds that the facts of the current case are materially different from the earlier case, so the earlier holding does not control. This is the most common technique.
Limiting: The court accepts the prior holding but reads it narrowly, refusing to extend it to new situations beyond its original facts.
Overruling: The court explicitly says the prior case was wrong and will no longer be followed. This is rare and requires explicit acknowledgment.
"Adherence to precedent is usually the wise policy, because in most matters it is more important that the applicable rule of law be settled than that it be settled right."
— Burnet v. Coronado Oil & Gas Co., 285 U.S. 393, 406 (1932) (Brandeis, J., dissenting)Understanding which court's decisions bind which other courts requires understanding the hierarchy of the system. In the federal system, there are three levels. Authority flows downward: every court is bound by every court above it.
Because each federal circuit creates its own binding precedent, two circuits can reach opposite conclusions on the same legal question. This is called a circuit split. When a circuit split exists, the law is literally different depending on which state you are in — a situation that only the Supreme Court can resolve by granting certiorari and issuing a uniform national ruling.
When checking a citation for a federal case, the reporter (F., F.2d, F.3d, F.4th for Courts of Appeals; F. Supp. for District Courts) tells you the level of the court. A case in F.4th is binding in its circuit; a case in F. Supp. is not binding on any other court.
Every state has its own court system operating independently of the federal courts. State courts handle the vast majority of litigation in the United States — family law, contracts, property, most criminal matters. State court decisions interpret state law, and the state's highest court has the final word on what that state's law means.
The federal courts have no authority to overrule a state supreme court's interpretation of that state's own law. The U.S. Supreme Court can only intervene when a federal constitutional question is present.
The federal and state court systems are parallel, not nested. A state court case about a contract dispute has no connection to the federal courts unless a federal legal question arises. When a case involves both state and federal law, the state court applies state law on state questions and federal constitutional law as interpreted by the U.S. Supreme Court on federal questions.
Federal courts sometimes apply state law (e.g., in diversity jurisdiction cases). When they do, they must predict what the state's highest court would hold — they cannot create binding state law precedent themselves.
When federal and state law conflict, federal law prevails under the Supremacy Clause (U.S. Const. art. VI, cl. 2). State courts are bound by the U.S. Supreme Court on federal constitutional questions regardless of what state law says.
A statute is written down once — in a code, enacted by a legislature, organized by subject. A court opinion works differently. It is written by a judge in a specific case, then collected and published in volumes called reporters. Each reporter collects opinions from a particular court or set of courts in chronological order. To find the opinion, you need to know which reporter it is in, which volume, and which page.
This is the analogy that makes reporter-based citations click: just as 42 U.S.C. § 1983 tells you exactly where to find a statute in the United States Code (Title 42, Section 1983), a case citation like 347 U.S. 483 tells you exactly where to find an opinion in the United States Reports (Volume 347, page 483). Both are addresses in a numbered, organized collection of legal text.
The difference is that statutes are organized by subject, while reporters are organized by time — the order opinions were decided. You cannot look up cases by topic in a reporter; you need the citation to go directly to the page.
Every case citation is a structured address. Once you know what each part means, you can decode any citation and find the opinion it refers to.
To see why citation format matters, compare a case citation to a statute citation:
Both citations are addresses in numbered collections. Both let anyone — in any library, using any source — find the exact text being cited. That is the point of citation: it makes legal knowledge verifiable, shareable, and permanent.
Whether you are citing a case or a statute, the structure and format requirements are precise. A wrong reporter abbreviation, a missing pincite, or an incorrect year can make a citation unverifiable — and in a legal proceeding, an unverifiable citation carries no weight. Cite Commons checks your citations against five major citation guides so you can be confident your legal knowledge travels where you intend it to go.