Laws can come in several forms. The two most common types are session laws or codes. A single session law can cover a wide variety of subjects and is not necessarily assembled in any logical order.
Session laws are mostly useful for historical research.
A code generally means a subject compilation of all general laws in force at the time of publication. Every time a legislative body passes a session law, the code is edited to reflect the changes. Many state statutory publications also have popular name indexes. The Law Library has the codes and session laws for all fifty states and the federal government. Finding a session law without a correct or complete citation is not difficult if you know the subject matter of the law.