Definition
Case law is the body of law derived from judicial decisions — opinions issued by courts in the course of resolving actual disputes — as distinguished from law created by legislatures (statutes), administrative agencies (regulations), or constitutions. It represents the accumulated interpretive and precedential output of the judiciary over time.
Case law operates through the doctrine of stare decisis: courts deciding new disputes look to prior decisions (precedents) that addressed similar legal questions and, with exceptions, follow those earlier rulings. In this way, individual decisions aggregate into a body of law that guides future courts, lawyers, and parties.
Case law performs several functions simultaneously:
(1) It announces legal rules in areas where legislatures have not acted — particularly in common law fields such as tort, contract, and property.
(2) It interprets statutes, constitutional provisions, and regulations, giving those texts concrete meaning as applied to real facts.
(3) It fills gaps left by written law, sometimes generating rules that persist until legislatures intervene.
Common Language
Modern common usage (Wiktionary): Law developed by judges through court decisions and opinions, as distinct from statute and other legislation.
The common usage is accurate as far as it goes, but it understates the structural role case law plays. In ordinary speech, "case law" often functions as a synonym for "what the courts have said" — useful shorthand when distinguishing judicial from legislative authority. In legal research, the term carries additional weight: case law is not merely illustrative of law but is, in common law systems, a primary source of law in its own right. A statute on point does not automatically displace case law; the two interact, and case law interpreting a statute becomes part of the law governing that statute until overruled or superseded.
Common Confusion
Case law is sometimes used interchangeably with common law, but the terms are not synonymous. Common law refers specifically to judge-made law developed in the absence of statutory authority — law created entirely through judicial decision-making. Case law is broader: it encompasses all judicial decisions, including those that interpret statutes, apply constitutional provisions, or gloss regulatory language. Every common law rule lives in case law, but not all case law is common law. A researcher searching for "case law on breach of contract" may be looking at a mix of common law doctrine and statutory interpretation; conflating the two categories can obscure where the governing rule actually originates.
Why It Matters in Research
Case law is the primary medium of legal research in common law systems, and navigating it well requires understanding several structural features of the Law Mind corpus.
Temporal layering matters enormously. A case decided in 1880 may state a rule that has since been modified by statute, overruled by a higher court, or distinguished into irrelevance. Historical sources — including the dictionary entries underpinning this entry — reflect the law as it stood at the time of their drafting. Bouvier's and the early Black's editions predate many statutory reforms and constitutional developments; their case law references are starting points for historical research, not current authority.
Jurisdictional hierarchy shapes everything. Case law is not a single unified body. Federal and state court systems generate parallel streams of precedent. A decision of the Supreme Court of the United States on a federal question binds all courts; a state supreme court's ruling on state law binds courts within that state. Researchers must identify which court's case law governs the question before them — a step historical dictionaries, written without jurisdiction-specific focus, often skip.
Reported versus unreported decisions. Historical sources uniformly refer to "reported cases" as the substance of case law. This was a meaningful filter when reporting was selective and expensive. In the modern corpus, the distinction has eroded: digital databases include opinions that were never formally "reported" in traditional reporters. Researchers using historical dictionary definitions of case law should recognize that those definitions implicitly excluded much that modern databases now capture.
The Law of the Case Doctrine (civpro_100) is a distinct concept that occasionally creates confusion: it refers to a procedural rule binding a court to its own prior rulings within a single litigation, not to the broader body of precedent that constitutes case law.
Historical Dictionary Support
The historical dictionaries converge on the core definition: case law is the aggregate of reported judicial decisions forming a body of jurisprudence, as distinguished from statutes and other sources. Black's (both editions) and Bouvier's are consistent on this point, and the formulation is clean enough that it has not required substantial revision.
Bouvier's adds a useful structural observation absent from Black's: case law can be divided into decisions of regularly organized courts on one hand, and other adjudicative bodies on the other. This distinction matters for researchers working in administrative law or in periods when court organization was less standardized.
What the historical sources do not address is the interplay between case law and statutory interpretation — the modern reality that much of what appears in judicial opinions is neither pure common law nor mere case reporting, but judicial construction of legislative text. Historical dictionaries treat case law and statute law as parallel but separate tracks. Contemporary practice recognizes them as deeply entangled, with case law on statutory meaning sometimes carrying as much governing force as the statute itself.
Jurisdictional Note
In civil law jurisdictions (including Louisiana at the state level and many non-U.S. systems), judicial decisions are not formally binding precedent and case law does not carry the same primary-source authority it holds in common law systems. Researchers extending common law case law concepts into civil law contexts should treat the term with caution; the structural role of judicial decisions differs fundamentally.
Encyclopedia Cross-Reference
Law of the Case Doctrine — The Law Mind Civil Procedure & Evidence Encyclopedia (civpro_100)