The Code of Federal Regulations is the official codification of "general and permanent" rules and regulations promulgated and enforced by Executive Departments and Agencies of the United States Government as might be authorized by Federal Statutes (which, in turn, can be found within both the Statutes at Large and the United States Code).
Such Federal rules and regulations- so long as they are not Classified for purposes of security- are published daily (except holidays) as part of the Federal Register which, since its inception in 1936, is- for all intents and purposes- the official Journal of the Executive Branch of the U.S. Government (thus, the Federal Register has the same relationship as a "record" of the formal activities of that branch of the Federal Government to said branch as has the Congressional Record to the Legislative Branch [that is: both houses of the Congress of the United States]). It should here be noted that the Federal Register also includes proposed Federal rules and regulations that have not yet been adopted as well as notices of administrative meetings and proceedings within the Executive Branch.
Even as the Federal Register was first being published, however, it was already clear that a codification of such rules and regulations as actually had been adopted would be most desirable, as such a compilation would make said rules and regulations still in force at any given time all the more easier to locate (in much the same manner that it is much easier to locate a particular Federal Statute in the United States Code than within the Statutes at Large). Thus, in 1938, began the publication of the Code of Federal Regulations (aka CFR).
The CFR mimics the United States Code in that it, too, consists of 50 Titles which, at least at the start, were- more or less- to be arranged alphabetically; this is no accident, by the way: the original idea was that each Title of the Code of Federal Regulations would likely contain the rules and regulations associated with the subject matter of the same numbered Title of the USC. However, as one can see from the table following this explanatory section, this original plan was ignored from the very beginning and, therefore, a Title in the CFR is not always going to match up with the Subject matter of the same Title number in the USC. In addition- unlike as is the case with the United States Code, in which the Titles are, for the most part, intended to be permanent (although the names of said Titles can always be altered, as needed)- not all Titles of the CFR are necessarily utilized at all times and new purposes for any CFR Title numbers no longer in use may later be found (the United States Code, by the way, has only just started this practice when a no longer used Title 6 became, relatively recently, that for 'Homeland Security'): during a period when a given Title number of the CFR is not actually in use, it is said to be "Reserved" [as of this typing (mid-2010), this is the status of only one CFR Title: Title 35].
The CFR is published in full annually in four separate volumes, one new volume issued every three months (Titles 1 through 16 in January; Titles 17 through 27 in April; Titles 28 through 41 in July; and Titles 42 through 50 in October). Individual provisions of the Code of Federal Regulations are cited as X CFR y where 'X' is the Title and 'y' the number of the rule/regulation (as Part and section of the given Title, separated by a decimal point: thus 47 CFR 97.13 would be section 13 of Part 97 of Title 47 of the Code of Federal Regulations [this, by the way, a regulation that happens to govern an aspect of Amateur Radio in the United States]).
The courts are expected to interpret the provisions of the CFR in the same manner in which they interpret Federal Statutes; indeed, any provision of the CFR is considered- in judicial, no less than in administrative, proceedings- as legally binding as any Federal Statute, but only if the given rule or regulation therein is a "reasonable interpretation" of the specific statute(s) enabling said rule or regulation (this is known as the "Reasonable Interpretation" rule). While judicial notice is required to be taken of the contents of the Federal Register (per 44 USC 1507), the Code of Federal Regulations is taken to be the "best legal evidence" of the actual text of the Federal rules and regulations in force at any given time (per 44 USC 1510).
The compilation of the Code of Federal Regulations has been arranged as in the following table:
|Title||Subject Matter of Title||Years so utilized||same subject as numbered U.S. CODE Title?|
|Grants and Agreements||2005--||No|
|Accounts and Budget||1944||No|
|8||Aliens and Citizenship||1938-1941||related|
|Aliens and Nationality||1942--||Yes|
|9||Animals and Animal Products||1938--||No|
|10||Army: War Department||1938-1946||related|
|12||Banks and Banking||1938--||Yes|
|Business Credit and Assistance||1957--||No|
|Aeronautics and Space||1960--||No|
|Commerce and Foreign Trade||1949--||related|
|17||Commodity and Securities Exchanges||1938--||No|
|18||Conservation of Power||1938-1965||No|
|Conservation of Power and Water Resources||1966--||No|
|21||Food and Drugs||1938--||Yes|
|Highways and Vehicles||1967-1968||related|
|Housing and Housing Credit||1949-1971||No|
|Housing and Urban Development||1972--||No|
|Alcohol, Tobacco Products and Firearms||1973--||related|
|31||Money and Finance: Treasury||1938--||related|
|33||Navigation and Navigable Waters||1938--||Yes|
|National Military Establishment||1949||No|
|35||Panama Canal||1938-2000 [discontinued]||No|
|36||Parks and Forests||1938-1948||No|
|Parks, Forests and Memorials||1949-1973||No|
|Parks, Forests and Public Property||1974--||No|
|37||Patents and Copyrights||1938-1946||No|
|Patents, Trademarks and Copyrights||1947--||No|
|38||Pensions, Bonuses and Veterans' Relief||1938--||related|
|Protection of Environment||1972--||No|
|Public Contracts and Property Management||1965--||related|
|43||Public Lands: Interior||1938--||related|
|44||Public Property and Works||1938-1972||No|
|Emergency Management Assistance||1979-1989||No|
|Emergency Management and Assistance||1990--||No|
|48||Territories and Insular Possessions||1938-1957||Yes|
|Trade Agreements and Adjustment Assistance Programs||1964-1968||No|
|Federal Acquisition Regulation System||1984-1989||No|
|Federal Acquisition Regulations System||1990--||No|
|49||Transportation and Railroads||1938-1948||related|
|Wildlife and Fisheries||1961--||No|