What Is the Simple Definition of Case Law?
Case law is the body of law created by written court decisions rather than by legislatures. When a court decides a dispute and explains its reasoning in a published opinion, that reasoning becomes a rule that other courts can apply in later cases raising the same question. Lawyers also call it judge-made law, decisional law, or common law.
Case law works alongside the other primary sources of American law: constitutions, statutes passed by legislatures, and regulations issued by agencies. Courts produce case law in two main ways. First, they interpret those written sources, settling what an ambiguous phrase in a statute or constitution means. Second, in areas the legislature never codified, such as much of tort and contract law, courts develop the governing rules themselves, decision by decision, a tradition American law inherited from the English common law.
Not every decision makes case law. Trial courts resolve thousands of disputes that end with a verdict and no published opinion. The case law that matters most comes from appellate courts, whose published opinions bind the courts below them. If a term in this guide is unfamiliar, our legal dictionary defines the vocabulary courts use.
What Is an Example of Case Law?
The clearest example is Miranda v. Arizona, 384 U.S. 436 (1966). No statute required police officers to tell suspects about their rights before questioning them in custody. The rule exists because the Supreme Court decided a case: it held that statements obtained through custodial interrogation are inadmissible unless the suspect was first warned of the right to remain silent and the right to an attorney. Every “Miranda warning” read since 1966 traces back to that single opinion, not to an act of Congress.
Most case law is less famous and more practical. Suppose a state statute increases penalties for theft of a “motor vehicle,” and someone is charged after stealing an e-bike. Is an e-bike a motor vehicle? The statute may not say. When the state’s appellate court answers that question in a published opinion, its answer becomes case law, and every trial court in the state must follow it the next time the question comes up. Thousands of questions like this get settled every year, which is why reading the statute alone is never the end of legal research.
Is It ‘Caselaw’ or ‘Case Law’?
Both spellings are in circulation, and both are understood. “Case law” as two words remains the standard form in most dictionaries, style guides, and formal legal writing. The one-word “caselaw” has gained ground in recent decades and appears in some court opinions and legal databases. If you are writing for a class, a court, or an employer, the two-word form is the safe choice; no reader will fault you for it.
Why Do Lawyers Use Case Law?
Because courts follow precedent, past decisions are the best available evidence of how a court will rule the next time. That gives case law three practical jobs in a lawyer’s work:
- To bind the court. If a higher court in the same jurisdiction has already decided the question, citing that decision tells the judge the outcome is not open for debate.
- To give statutes their working meaning. Legislatures write in general terms; cases show how those terms apply to specific facts. A lawyer who reads only the statute knows the rule in theory. A lawyer who reads the cases knows how it actually operates.
- To predict and persuade. Where no binding precedent exists, lawyers assemble persuasive decisions from other courts and argue by analogy, showing that their client’s facts line up with cases that came out the right way.
Law students learn to work with opinions the same way, which is why case brief format and samples are among the first things taught in law school.
How Precedent and Stare Decisis Work
The engine behind case law is stare decisis, Latin for “to stand by things decided.” The doctrine holds that courts should follow the rules laid down in earlier decisions rather than relitigating every question from scratch. It is what makes the law predictable: parties can order their affairs knowing how courts have treated similar disputes.
Two distinctions do most of the work:
- Binding versus persuasive authority. A decision is binding only on courts below the deciding court in the same jurisdiction. A federal trial court in Ohio must follow the Sixth Circuit and the U.S. Supreme Court; a decision from the Ninth Circuit is merely persuasive. State courts are bound by their own state’s appellate hierarchy, not by other states’ courts.
- Holding versus dicta. Only the holding, the rule necessary to resolve the dispute actually before the court, binds later courts. Everything else in an opinion, however interesting, is dicta and only persuades.
Precedent is strong, but not permanent. A court can distinguish an earlier case by showing the facts differ in a way that matters, and the court that issued a precedent (or a higher one) can overrule it outright. That is rare and consequential, which is why researchers always verify a case is still good law before relying on it. Overruled or criticized decisions are exactly what citators are built to flag.
Case Law vs Statutory Law
Statutory law is enacted by a legislature as general, forward-looking text. Case law is made by courts one dispute at a time. The two constantly interact: courts interpret statutes, and legislatures respond to court decisions by amending statutes.
| Case law | Statutory law | |
|---|---|---|
| Who makes it | Courts, in written opinions | Legislatures (Congress, state legislatures) |
| How it develops | Incrementally, case by case | By enactment and amendment |
| Where it lives | Reporters and opinion databases | Codes (e.g., the United States Code) |
| Scope | Tied to the facts decided | General rules stated in advance |
| How it changes | Distinguished or overruled by courts | Amended or repealed by the legislature |
Neither source outranks the other across the board. A valid statute displaces earlier common-law rules on the same subject, but courts decide what the statute means, and courts can strike down statutes that violate a constitution. For how the two meet in practice, see our guide to finding statutes, codes, and regulations.
How to Find Case Law
Reading about case law only gets you so far; at some point you need the opinions themselves. The good news is that you no longer need a paid subscription for most research. Free databases now cover federal and state appellate opinions in depth, and our guide to how to find case law free compares them and walks through the search strategy law librarians teach. If you prefer to start with a tool you already know, the Google Scholar case law search is the fastest on-ramp.
Where you look also depends on the court. Federal opinions are centralized; state-court publishing varies widely, so we keep a state-by-state guide to case law by state. And for the full library of legal-research guides beyond case law, start at the Legal Journal homepage.