The United States Code is meant to be an organized, logical compilation of the laws passed by Congress. At its top level, it divides the world of legislation into fifty topically-organized Titles, and each Title is further subdivided into any number of logical subtopics. In theory, any law -- or individual provisions within any law -- passed by Congress should be classifiable into one or more slots in the framework of the Code. On the other hand, legislation often contains bundles of topically unrelated provisions that collectively respond to a particular public need or problem. A farm bill, for instance, might contain provisions that affect the tax status of farmers, their management of land or treatment of the environment, a system of price limits or supports, and so on. Each of these individual provisions would, logically, belong in a different place in the Code. (Of course, this isn't always the case; some legislation deals with a fairly narrow range of related concerns.)
The process of incorporating a newly-passed piece of legislation into the Code is known as "classification" -- essentially a process of deciding where in the logical organization of the Code the various parts of the particular law belong. Sometimes classification is easy; the law could be written with the Code in mind, and might specifically amend, extend, or repeal particular chunks of the existing Code, making it no great challenge to figure out how to classify its various parts. And as we said before, a particular law might be narrow in focus, making it both simple and sensible to move it wholesale into a particular slot in the Code. But this is not normally the case, and often different provisions of the law will logically belong in different, scattered locations in the Code. As a result, often the law will not be found in one place neatly identified by its popular name. Nor will a full-text search of the Code necessarily reveal where all the pieces have been scattered. Instead, those who classify laws into the Code typically leave a note explaining how a particular law has been classified into the Code. It is usually found in the Note section attached to a relevant section of the Code, usually under a paragraph identified as the "Short Title".
