Identifying the rules that apply to a particular legal issue in your jurisdiction requires legal research. The legal research process involves not only locating legal authorities, but also determining their relevance.
Primary v. Secondary
Legal researchers utilize two types of authority, referred to as primary and secondary authority.
Primary authority is the law, which includes constitutions, statutes and ordinances, rules and regulations, and case law. These authorities form the rules that courts follow.
Secondary authority is not the law. Secondary authorities, such as legal dictionaries and encyclopedias, books and treatises, and journal articles, explain and analyze the law and help researchers both understand and locate primary authorities.
Mandatory v. Persuasive
Authorities that courts must follow are called mandatory (or binding) authority.
Authorities that courts may follow if persuaded to do so are called persuasive (or non-binding) authority.
Secondary authority is always persuasive. Primary authority (the law) may be mandatory or persuasive depending upon the jurisdiction where the dispute is to be decided and the level of the court that decided a particular case.
State Law Issue
State courts apply state statutes and regulations and follow precedent from that state. For example, South Carolina courts must apply South Carolina statutes, regulations, and case law. If a South Carolina court has not ruled on a particular legal issue, it may be persuaded by a decision from a Georgia court.
Federal Law Issue
For issues of federal law, federal courts apply federal statutes and regulations and precedent from federal courts in their circuit. If a federal court has not ruled on a particular legal issue, it may be persuaded by a decision from a different federal circuit.
United States Supreme Court decisions are mandatory on issues of federal law for all state and federal courts.
Level of Court
Whether or not a decision (case) is mandatory or persuasive within a particular jurisdiction (state or federal) depends upon the level of the court that decided it.
State and federal courts typically follow the court structure depicted in the diagram below. Trial court decisions are not mandatory for any court. Intermediate appellate court decisions are mandatory for the trial courts below. Decisions of the highest appellate court or court of last resort are mandatory for both the intermediate appellate courts and trial courts below.
The South Carolina Supreme Court is our court of last resort. Its decisions are mandatory for our intermediate appellate court, the South Carolina Court of Appeals, and all South Carolina trial courts. Decisions of the South Carolina Court of Appeals are mandatory for South Carolina trial courts only.
Decisions of the South Carolina Supreme Court may be appealed to the United States Supreme Court if accepted via writ of certiorari on an issue of federal law.
The federal court system is divided into eleven numbered circuits, the District of Columbia, and the Federal Circuit. The decisions of the United States Supreme Court are mandatory for all federal circuit courts of appeals and all federal district courts. The decisions of the courts of appeal for each of these circuits are mandatory for the federal district (trial) courts within that circuit.
With a basic understanding of the structure of the U.S. legal system, the available sources of law, and the application of weight of authority, you will be prepared to evaluate the resources you find as you conduct your legal research (see diagram below).