Legal Definitions - case law

Case law refers to the body of legal principles and rules that come from judges' decisions in individual court cases, rather than from laws passed by legislatures (known as statutes) or rules created by government agencies (known as regulations).

When judges decide a case, especially when interpreting existing laws or applying them to unique situations, their rulings can set a precedent. This means that future courts facing similar facts or legal questions will look to these prior decisions for guidance. Case law, sometimes used interchangeably with "common law," is essentially the law developed and refined through the courts' interpretations and applications over time, providing specific meaning and context to broader legal principles.

• Example 1: Defining "Unreasonable Search"

  Imagine a scenario where a new type of drone technology is used by law enforcement to gather evidence without a warrant. The Fourth Amendment to the U.S. Constitution protects against "unreasonable searches and seizures," but it doesn't specifically mention drones. If a court rules that using this drone technology in a particular way constitutes an "unreasonable search," that decision becomes case law. Future courts in that jurisdiction, when presented with similar facts involving drone surveillance, would refer to this precedent to determine whether a search was lawful. This illustrates how case law adapts constitutional principles to new technologies and situations.

• Example 2: Interpreting a Broad Environmental Statute

  Consider a state law that broadly prohibits "significant pollution" of waterways. A manufacturing company is accused of releasing a new chemical compound into a river. The statute doesn't list this specific chemical, nor does it precisely define "significant pollution" in all contexts. A court's decision in this case, after hearing expert testimony and considering the impact of the chemical, might establish a legal definition or threshold for what constitutes "significant pollution" for that particular compound or similar substances. This ruling would then serve as case law, guiding environmental agencies and other courts in future enforcement actions or disputes involving similar pollutants, even before the legislature updates the statute.

• Example 3: Establishing Liability for Online Content

  Suppose a social media platform is sued because a user posted defamatory content that caused harm to another individual. Existing defamation laws were primarily written for traditional media like newspapers or television. A court's decision in such a case might clarify the extent to which online platforms are responsible for content posted by their users, or under what circumstances they must remove harmful material. This judicial interpretation would create case law, providing guidance for other courts and for technology companies on their legal obligations regarding user-generated content, filling gaps where statutes might be silent or ambiguous about digital platforms.