If you are researching a statutory issue, it is rare that the text of the statute alone will answer your research question.  You will most likely need to look for cases interpreting the statute.  Using the annotations in a code is one of the best ways to identify such cases interpreting a statute.

The U.S. Code is published by the federal government, but attorneys generally use an annotated version of the code from Lexis or Westlaw when doing legal research. These annotated codes include the text of the law plus annotations such as:

• Historical Notes (or credits) for the statute
• Cross References to other relevant sections of the code
• Administrative Law citations (e.g., CFR)
• Secondary Sources (e.g., legal encyclopedias, treatises, forms, and other practice materials)
• Notes of Decisions (selective list of the most important cases)
• Topic/Key Numbers for case law research (West annotated codes only)

Start with resources selected by editors of the annotated codes. 

• For interpretive cases, use the Notes of Decisions on Westlaw or Citing Decisions on Lexis.
• For interpretive secondary sources, use the Context & Analysis tab on Westlaw Edge or the Research References & Practice Aids section on Lexis Advance (located at the bottom of the page).

Use citators such as KeyCite/Citing References on Westlaw or Shepard’s on Lexis to see all cases citing to a specific statute section.  Use the jurisdiction filter and/or the “search within results” feature to narrow your results.