Statutes are laws written and enacted by the legislative branch of government.  Most new laws are created through statutes (as opposed to being created by judges through common law).

At the Federal level, each statute is published in three versions:

1. First, a statute is enacted as a slip law, which is the statute by itself on a single sheet or in pamphlet form.  When a slip law is published, it will be given a Public Law Number to identify it. The Public Law Number (e.g. Pub.L. No. 111-2) consists of two parts:  the first number represents the number of the Congress which passed the law ; the second number represents the chronological order in which the law was passed.  In the above example, we have the 2nd law passed by the 111th Congress.  Slip laws/Public Laws are available in print or online through the Library of Congress's Thomas Web site.
   
   
2. Next, the statute is published as a session law.  Session laws are the slip laws bound chronologically by Congressional session (each Congress lasts two years and is divided into two sessions).  U.S. Statutes at Large is the official publication of Federal session laws.
   
   
3. Finally, the law is published as code.

There are several problems with researching statutes using slip laws or session laws.  First, usually you will be searching by subject, and neither slip laws nor session laws are arranged by subject.  Second, a statute may cover several subjects, and the subject matter you are looking for may not be apparent from the title of the statute.  For example - would it be obvious from looking at the title of the Health Care and Education Reconciliation Act of 2010 that this statute includes tax law provisions?  Third, for each time a statute is amended, a separate Public Law must be passed, so you may have to read through several slip laws to get the complete and current version of a statute's language. Finally, from looking at slip laws or session laws, there's no way to tell if a statute has been repealed.

Therefore, when researching, you'll want to use the third version of a statute, which is called the code.  A code arranges the statutes by topic (rather than chronologically), indexes them to allow for subject access, and incorporates any amendments and repealed language to always give you the current state of the law.

The official codification (i.e. the version published by the government) of U.S. Federal statutes is the United States Code (U.S.C.).  U.S.C. is broken down into 51 subject Titles, with each Title representing a major subject area (e.g. Banks and Banking, Labor, Transportation).  U.S.C. is published in full every six years - the most recent is 2006 - with cumulative bound supplements issued each year in between that allow you to update.  Publication may lag several years.  Because of these long delays, and because U.S.C. doesn't contain any explanatory material to help researchers understand the statutory language, it's better to research using an unofficial code - a commercially-published version of the Code.  Unofficial codes include references (called "annotations") to primary and secondary sources which relate to each code section, and are updated much more frequently than U.S.C. 

There are two unofficial versions:  United States Code Annotated (U.S.C.A., published by West) and United States Code Service (U.S.C.S., published by Lexis).  Both sets include the entire U.S. Code, as well as other material (e.g. the Constitution, Federal Court Rules, Federal Rules of Evidence).  Everything is annotated, with references to case law and secondary sources (such as law reviews, treatises, and ALR articles) interpreting the statutory language, plus cross-references to related regulations.  Both versions also include multi-volume indexes at the end of the set, along with a Popular Name Table that allows you to search for a Code section when you know the name of the statute (e.g. the USA PATRIOT Act, Megan's Law).  Both versions also include volumes that contain tables showing parallel references for public laws, session laws, and code sections. Both versions are updated annually with pocket parts and/or softbound pamphlet supplements (just as we saw with the Digests), and both include advance legislative service volumes which show changes to the Code sections in between the times when the pocket parts are issued.  You can also use an online citator to determine if your statute is still valid and to find cases and other materials that analyze or interpret the statutory language.  Use KeyCite (in Westlaw) for U.S.C.A and Shepard's (in Lexis) for U.S.C.S.

The Kalamazoo College Library does not have any printed versions of the U.S. Code. You must search Westlaw for the current U.S. Code.

There are some differences between the two official versions of the Code: 

1. U.S.C.A. seeks to be comprehensive in its case annotations, including every relevant case that discusses the statute, while U.S.C.S. includes only selected cases in its annotations.
2. While both sets include references to related administrative regulations, only U.S.C.S. includes references to cases decided by administrative law courts (U.S.C.A. does not).
3. While both sets include references to law journal articles, ALR annotations, and AmJur articles, there are differences in the coverage of secondary source materials in the annotations.  Since U.S.C.A. is published by West publishing, you will find references to print treatises published by West publishing, but not to those published by Lexis publishing.  Additionally, C.J.S. is included only in U.S.C.A.  Likewise, since U.S.C.S. is published by Lexis, it will contain references to print treatises published by Lexis but not those published by West.  
4. Since it is published by West, U.S.C.A. has references to the West Topic and Key Number system, while U.S.C.S. does not.

Therefore, if you have access to both U.S.C.A. and U.S.C.S., it's a good idea to check your statute in both sets to ensure that you aren't missing a potentially relevant source.