Know that the U.S.is a common law country that derives our legal system from England. Jargon handout 1. Laws created by a branch of the government or government body acting in its lawmaking capacity are primary legal authority.
Legislation is enacted to govern future situations.
If no legislation applies, courts develop and apply a judge-made rule of law. Anything other than primary authority that a court could use as a basis for decision. This does not have the force of law. Secondary authority can never be more than persuasive authority. Restatements of the Law Dictionaries 3.