How to Research U.S. Law

Effective legal research in the United States requires navigating a multi-layered system of primary and secondary sources, each carrying distinct authority. This page explains how that research process works — covering the major source types, standard research workflows, and the boundaries that distinguish one type of legal authority from another. Understanding these distinctions is essential whether the task involves verifying a statutory requirement, tracing regulatory authority, or interpreting how courts have applied a rule.

Definition and scope

Legal research is the process of identifying and retrieving legally binding or legally persuasive materials relevant to a specific question of law. In the U.S. context, that task spans at least 4 distinct layers of law: constitutional provisions, statutes, regulations, and judicial decisions.

The sources of U.S. law fall into two broad categories:

• Primary authority — the law itself. This includes the U.S. Constitution, federal and state statutes, federal regulations published in the Code of Federal Regulations (CFR), and binding court opinions.
• Secondary authority — materials that explain, analyze, or synthesize primary law. This includes law review articles, legal encyclopedias such as American Jurisprudence (AmJur), Restatements published by the American Law Institute (ALI), and treatises.

The scope of any research question determines which layer dominates. A dispute over a federal agency's rulemaking authority starts in the CFR and the enabling statute. A contract dispute between private parties in a single state will center on that state's statutory code and its appellate court decisions.

Constitutional law foundations sit at the apex of every research hierarchy: no statute, regulation, or court ruling can stand if it conflicts with the U.S. Constitution as interpreted by the Supreme Court.

How it works

Legal research follows a structured sequence. Skipping layers produces incomplete or misleading results.

1. Frame the legal question. Identify the jurisdiction (federal, state, or both), the type of dispute (civil, criminal, regulatory), and the applicable area of law — such as employment law, tort law, or immigration.

2. Locate controlling constitutional authority. Determine whether constitutional provisions — federal or state — govern the issue. The Constitution of the United States, maintained by the National Archives, and annotated versions published by the U.S. Senate and House are authoritative public sources.

3. Identify the governing statute. The United States Code (U.S.C.), maintained by the Office of Law Revision Counsel (OLRC) at uscode.house.gov, is the official codification of federal statutory law. State codes are maintained by individual state legislatures and often accessible through state legislature websites.

4. Find implementing regulations. Federal agencies publish rules in the Federal Register and codify them in the CFR, available at ecfr.gov through the Government Publishing Office (GPO). The CFR is organized into 50 titles by subject area — Title 26, for example, covers the Internal Revenue Code's regulatory implementation.

5. Research case law interpreting the statute or regulation. Federal opinions at the district, circuit, and Supreme Court levels are available through the Government Publishing Office and through the Legal Information Institute (LII) at Cornell Law School (law.cornell.edu). Understanding how federal law is made helps contextualize how courts interpret legislative intent.

6. Consult secondary sources for synthesis. Secondary sources do not create law but assist in understanding it. The ALI's Restatements summarize common law principles across jurisdictions. Law review articles published by accredited law schools often analyze circuit splits or statutory ambiguities that primary sources leave unresolved.

7. Verify currency. Statutes are amended; regulations are updated; decisions are reversed or distinguished. Citator services — most prominently Westlaw's KeyCite and LexisNexis's Shepard's — track subsequent history, though free equivalents with partial coverage exist through Google Scholar and CourtListener (courtlistener.com), operated by the nonprofit Free Law Project.

Common scenarios

Scenario 1: Researching a federal regulatory requirement. An entity subject to the Occupational Safety and Health Act (OSH Act, 29 U.S.C. § 651 et seq.) would begin with the statute on the OLRC database, then locate implementing regulations under 29 CFR Parts 1900–1999 on ecfr.gov, then review OSHA's published enforcement guidance on osha.gov. Relevant administrative decisions from the Occupational Safety and Health Review Commission (OSHRC) constitute binding administrative precedent within that regulatory scheme.

Scenario 2: Researching state common law. A negligence claim governed by state law requires locating the state's appellate court decisions defining the duty, breach, causation, and damages elements. Because common law and case law develop through court decisions rather than statutes, the research is primarily opinion-driven, supplemented by the Restatement (Third) of Torts (ALI).

Scenario 3: Cross-jurisdictional conflict. When federal and state law address the same subject, the Supremacy Clause of Article VI of the U.S. Constitution controls — federal law preempts conflicting state law. Identifying whether preemption applies requires reading both the federal statute and any savings clauses it contains, then comparing them against the state provision. The Supreme Court's preemption doctrine is extensively documented in its published opinions, accessible through supremecourt.gov.

Decision boundaries

Understanding what legal research can and cannot resolve prevents misapplication:

Binding vs. persuasive authority. A decision from the Ninth Circuit Court of Appeals is binding on federal district courts within the Ninth Circuit but is only persuasive authority in the Fifth Circuit. Decisions from state courts of one state carry no binding weight in another state's courts on state law questions. Federal vs. state court jurisdiction determines which court's precedents govern a given matter.

Primary vs. secondary authority. Secondary sources — treatises, law reviews, Restatements — cannot override a statute or binding judicial decision. They assist interpretation but do not independently control outcomes.

Mandatory vs. discretionary agency guidance. An agency's published regulation in the CFR carries the force of law when issued through notice-and-comment rulemaking under the Administrative Procedure Act (APA, 5 U.S.C. § 553). An agency's informal guidance document, FAQ, or policy statement typically does not carry the same binding force, a distinction the Supreme Court has addressed in Perez v. Mortgage Bankers Association, 575 U.S. 92 (2015) (supremecourt.gov).

Enacted law vs. legislative history. Committee reports, floor statements, and conference reports are legislative history, not enacted law. Courts consult them when statutory text is ambiguous, but under textualist interpretive approaches, they carry limited weight. The GPO makes congressional documents available at congress.gov and govinfo.gov.

For a structured orientation to the primary research tools and how they interconnect, the U.S. legal system topic context provides a mapped overview of how each layer of authority relates to the others.

References

• United States Code — Office of Law Revision Counsel (OLRC)
• Code of Federal Regulations — Electronic CFR (eCFR), Government Publishing Office
• Legal Information Institute (LII), Cornell Law School
• CourtListener — Free Law Project
• U.S. Supreme Court — Official Opinions
• Congress.gov — U.S. Congress Legislative Records
• GovInfo — Government Publishing Office
• OSHA — Occupational Safety and Health Administration
• American Law Institute (ALI) — Restatements
• Administrative Procedure Act, 5 U.S.C. § 553 — OLRC
• Perez v. Mortgage Bankers Association, 575 U.S. 92 (2015) — supremecourt.gov