Primary authority is a law that is used to support a proposition or persuade a court or other authority to be in favor of one’s position. It is important to cite primary authority (law) in a motion or brief. In the legislative branch, primary authority takes the form of statutes. In the judicial branch, primary authority takes the form of cases, and in the executive branch, regulations which are the product of administrative agencies are primary authority.
Secondary authority, by contrast, offers explanation and commentary on the law by scholars and practitioners. Secondary authority helps to explain the application of the law to a specific problem. Secondary authority is non-law. Anything that can be quoted, but is not law, is secondary authority. Reference works, such as a Restatement of Law, are not primary authority in a case, unless they are cited and followed by a court as authority for its holding or reasoning.