Academic Success Resources for Students: Sources of Law: Cases, Statutes, Secondary Sources and More

Primary Sources

Primary sources of law are constitutions, statutes, regulations, and cases. Lawmaking powers are divided among three branches of government: executive; legislative; and judicial. These three branches of government, whether federal or state, create primary sources of law.

  • The executive branch creates administrative law, which is published as regulations or executive orders and directives.
    • The President of the United States makes executive orders and directives.
    • Administrative agencies of the government (for example, the Environmental Protection Agency or EPA) makes rules and regulations.
  • The legislative branch creates laws ("statutes") that are passed and published as statutes.
  • The judicial branch creates law in the form of decisions, also called "opinions" and "cases," that are published in case reporters. 
    • Judges create and shape the "common law."
    • In a common law system, the law is expressed in an evolving body of doctrine determined by judges in specific cases, rather than in a group of prescribed abstract principles.
    • The common law grows and changes over time. 
    • An important element of common law is stare decisis, which means that courts are bound to follow earlier decisions ("precedents").

Where Does Law Come From? 

This online CALI lesson explains the separation of powers among the three branches of government.


Branches of the U.S. Government from the U.S. General Services Administration

This federal government website describes the three branches of the U.S. Government and how they work together and check and balance one another.

Secondary Sources

Secondary sources are plain-language writings about the primary sources of law, and they are a great place to start research on any legal topic.

  • They are not law and they are not binding on any court.
  • They organize and explain the primary law to make it more accessible and understandable.
  • Use secondary sources, like treatises, practice guides, legal encyclopedias, and law journal articles, to help you find and understand the primary law, and to point you to the important statutes and cases that you can rely on when writing briefs, and memoranda.
  • Secondary sources, especially law journals, may influence lawmaking.

Legal encyclopedias alphabetically organize brief articles on legal subjects. The two main legal encyclopedias with national scope are:

  • Corpus Juris Secondum (C.J.S.), available in print or on Westlaw; and
  • American Jurisprudence 2nd (Am. Jur. 2d), available in print or on Lexis and Westlaw.

The two main California legal encyclopedias are:

  • Witkin's Summary of California Law, available in print in the Research Alcove or on Westlaw and Lexis; and
  • California Jurisprudence (Cal. Jur. 3d), available in print in the Research Alcove or on Westlaw.