Uncodified Statutes
Only "general and permanent" laws are codified; the Code does not usually include provisions that apply only to a limited number of people (a private law) or for a limited time, such as most appropriation acts or budget laws, which apply only for a single fiscal year. If these limited provisions are significant, however, they may be printed as "notes" underneath related sections of the Code. The codification is based on the content of the laws, however, not the vehicle by which they are adopted; so, for instance, if an appropriations act contains substantive, permanent legislation (as is sometimes the case), the permanent provisions will be incorporated into the Code even though they were adopted as part of a non-permanent enactment.
Read more about this topic: United States Code