Primary Authority vs. Secondary Authority: What's the Difference?

The test is not how reliable or scholarly the source is. It is whether a government body with lawmaking power produced it. Legislatures produce statutes. Agencies produce regulations. Courts produce opinions. Constitutional conventions and ratifying bodies produce constitutions. Those are primary authority. Everything else — no matter how brilliant the author or how often courts quote it — is secondary.

That is why an unpublished, one-paragraph opinion from an intermediate appellate court is primary authority and a 200-page treatise chapter by the leading scholar in the field is not. The opinion is an exercise of judicial power. The treatise is commentary about exercises of judicial power.

A few sources sit awkwardly at the border. Legislative history — committee reports, floor statements, hearing transcripts — is government-generated material about a statute, but it is not itself law; courts treat it as an interpretive aid whose weight varies enormously by judge. Uniform and model acts, like the UCC or the Model Penal Code, are secondary until a legislature enacts them; once enacted, the enacted state version is primary. In a brief you cite Cal. Com. Code § 2201, not "UCC § 2-201." Similarly, when a court adopts Restatement (Second) of Torts § 402A, the primary authority is the case adopting it, and that is what you cite.

Primary authority splits again into mandatory (binding) and persuasive. Mandatory authority comes from a lawmaking body with power over your court on your issue. Persuasive primary authority is real law — just law from a jurisdiction that does not control your case.

Work through it in this order. First, whose law governs: state or federal, and if state, which state's? Second, within that jurisdiction, what is the hierarchy? A statute beats a common-law rule unless the statute is unconstitutional. A higher court's holding binds lower courts in the same system (vertical stare decisis). Third, is the case still good law? Shepardize or KeyCite before you rely on anything.

Some recurring rules students get wrong: a federal court sitting in diversity must apply state substantive law as declared by the state's highest court, Erie R.R. Co. v. Tompkins, 304 U.S. 64 (1938), and a federal court of appeals decision on state law does not bind the state's own courts. State courts are bound by the U.S. Supreme Court on questions of federal law, but not by lower federal courts. A decision of the Ninth Circuit does not bind the Fifth. And in most jurisdictions one panel of an intermediate appellate court binds trial courts below it, while a sister-state supreme court decision is only persuasive — often highly persuasive when your jurisdiction has no case on point.

Cite a secondary source when it does work that no case can do for you. Three situations justify it. First, there is no primary authority on point in your jurisdiction and you need to show the court what the majority rule is and why it makes sense. Second, the issue is genuinely novel or the law is in flux, and a scholarly article frames the competing approaches. Third, you need background a court will not supply — the history of a doctrine, the economics of an industry, statistics, or a technical explanation.

Weight varies by source. Courts routinely cite the Restatements, and treatises with real institutional standing: Wright & Miller's Federal Practice and Procedure on civil procedure, Moore's Federal Practice, Collier on Bankruptcy, Nimmer on Copyright, Corbin and Williston on Contracts, Prosser & Keeton on torts. Law review articles are cited less often but can carry weight when authored by a recognized expert; Warren and Brandeis, The Right to Privacy, 4 Harv. L. Rev. 193 (1890), is the classic proof that an article can reshape doctrine.

The framing matters as much as the source. Lead with your primary authority and use the secondary source to support it — "Section 90 of the Restatement (Second) of Contracts, which the Iowa Supreme Court adopted in [case], provides . . . ." Never open an analysis section with a treatise. A judge reading a brief that cites Am. Jur. before it cites a case concludes you could not find a case.

Legal encyclopedias — American Jurisprudence 2d and Corpus Juris Secundum — are excellent for orienting yourself in an unfamiliar field and terrible to cite. They state black-letter propositions at a level of generality that helps no one, and their footnotes are their real value: they collect cases from every jurisdiction. Mine the footnotes, read the cases, cite the cases.

The same applies to A.L.R. annotations, which survey how courts nationwide have resolved a narrow question. An A.L.R. annotation is one of the fastest ways to find persuasive out-of-state authority. It is not something you quote to a court.

Also never cite: headnotes, West key numbers, or case synopses. Those are editorial additions by the publisher, not part of the opinion, and quoting a headnote as though it were the court's language is a serious credibility error. Westlaw and Lexis are platforms, not authority. Practice guides, CLE materials, and bar journal pieces are fine for orientation and rarely appropriate to cite. Black's Law Dictionary is a legitimate citation for a defined term and is frequently cited by courts, but it cannot carry an argument.

The Bluebook organizes citation rules by source type, so knowing which bucket a source falls into tells you which rule to open. Cases are Rule 10. Statutes are Rule 12. Regulations and other administrative material are Rule 14. Constitutions are Rule 11. On the secondary side, books and treatises are Rule 15, periodicals including law reviews are Rule 16, and unpublished or forthcoming material is Rule 17. Restatements, model codes, and uniform acts are handled with the statutory material at Rule 12.9, not as books.

Two mechanical points recur on 1L memo grading. Student-written law review material is signaled by a designation before the title — "Note," "Comment," or "Recent Case" — which tells the reader an unnamed student wrote it and adjusts the weight accordingly. And abbreviations for periodicals come from Table 13, while case names use Table 6; guessing at abbreviations is the fastest way to lose easy points.

Signals do different work for the two categories. A direct-support citation to a case takes no signal. A secondary source that merely supports the proposition by analogy takes "see" or "cf.," and one you are contrasting takes "but see" or "contra." Use "see generally" for background sources, which is where most treatise citations belong.

This is one area where the honest answer is that local rules and professor preferences govern, and you must ask. Three variables drive the differences.

Court rules on unpublished opinions. In the federal appellate system, Fed. R. App. P. 32.1 permits citation of unpublished federal opinions issued on or after January 1, 2007, but individual circuits still restrict their precedential weight. State practice ranges from free citation to outright prohibition. Check the local rules before relying on an unpublished decision.

Legal writing course rules. Many 1L programs bar secondary sources on the first closed-universe memo entirely, then permit them later. Some require you to cite the Restatement whenever your jurisdiction has adopted it; others treat any secondary citation as a signal you gave up on research. Ask your professor directly rather than inferring.

Field norms. In constitutional law, patent law, and bankruptcy, courts cite treatises and articles routinely. In criminal procedure and evidence, the statute and rule text dominate. In state common-law tort and contract, the Restatements do heavy lifting. Match your citation practice to what judges in that field actually do, which you learn by reading how the opinions in your research cite their own sources.