Skip to main content

Secondary Sources

Secondary sources criticize, describe, discuss, and summarize the law found in primary law sources. (Primary law includes constitutions, laws, judicial opinions, and regulations.)

Types of Secondary Sources

Primary sources have documents that are "the law." The documents are created by bodies with legal authority. For example, cases are decided by courts; statutes are enacted by legislatures; regulations are issued by administrative agencies.

U.S. Supreme Court building





Secondary sources are all the materials that are about the law. They are written by lawyers, law professors, law students, independent authors, and publishers' staff writers. They are useful in understanding the law, but they are not the law. You can't go to jail for disobeying a treatise or failing to comply with a dictionary.

Law has many types of secondary sources, used for different purposes:

  • Casebooks are collections of edited cases and other materials used to explore different issues in classes. They are generally not used in research.
    photo of 4 casebooks
  • Study aids (including Hornbooks, outlines, and Nutshells) are used to get an overview of a topic. They are meant to complement what is covered in a class. See Study Aids for Law Students.
    photo of 6 study aids for contracts
  • Treatises (often many volumes) cover areas in depth. They are used to learn a lot about an area. Often researchers use tables of contents, indexes, or online searches to find a short section that covers a narrow question.

    photo of part of Williston on Contracts
  • Dictionaries define legal terms.
    Black's Law Dictionary
  • Legal encyclopedias attempt to cover all of U.S. law. They are used to get an overview of a field or to find general rules of law. They are heavily footnoted and so can be tools for finding cases.
    Am. Jur. 2d volumes
  • Law reviews and other legal periodicals publish articles with scholarly analysis of legal issues.
    law review issues



  • American Law Reports (A.L.R.) publishes articles called "annotations" that summarize cases from around the U.S. on specific topics.
    3 volumes of ALR 6th
  • Practice materials (including form books and various deskbooks and guides) offer practical guidance.
    Washington Civil Procedure Deskbook

A law library also includes many of the sort of "regular books" you might see in a bookstore or public library, such as works of journalism, history, or political commentary.

Discussions of legal issues are also found in blogs, law firm and government websites, and even Twitter, and so these newer media are secondary sources as well (although this guide doesn't cover them).

Photo credit: U.S. Supreme Court building from

Why Use Secondary Sources?

It is often useful to start your research by finding an on-point secondary source, especially for an unfamiliar area of law. But why? Why not just start searching for relevant cases or statutes? Well, as explained by Kent C. Olson in Legal Research in a Nutshell (13th ed. p. 25),

Primary sources such as statutes and cases can be confusing, ambiguously worded documents. Secondary sources are usually more straightforward and try to explain the law. They summarize the basic rules and the leading authorities and place them in context, allowing you to select the most promising primary sources to pursue.

In other words, starting with a secondary source is more efficient and will provide you with an understanding of the forest AND help you identify the most important individual trees.

If you would like additional instruction on secondary sources, check out this lesson on CALI (visit the law student restricted databases page if you need the CALI authorization code):

Related Gallagher Guides