When a bill is enacted into law, it may amend or repeal earlier laws, or it may create an entirely new or "freestanding" law. Recently enacted laws are first printed individually as separate statutes known as "slip laws." At the end of a Congress, the slip laws are sequentially compiled in the annual federal session law volumes known as the United States Statutes at Large . Most statutes are then broken down by subject matter and incorporated into the 54 volumes and five appendices of the United States Code . This report provides an overview of federal statutes in each of these forms, as well as basic guidance for congressional staff researching statutes. When an individual piece of legislation is enacted under the procedures set forth in Article I, Section 7 of the U.S. Constitution, it is characterized as a "public law" or a "private law" depending on its intended audience. The overwhelming majority of laws passed by Congress are public laws because they have general applicability to the whole of society and are continuing and permanent in nature. Private laws are enacted for the benefit of a named individual or entity (for example, private laws can be enacted to assist a citizen injured by a government program). Each newly passed law-- public or private --is assigned a number according to the order of its enactment within a particular Congress. This system began in 1957 with the 85 th Congress. Laws enacted prior to 1957 are cited by the date of enactment and the chapter number assigned to them in the Statutes at Large , discussed further below. When researchers want to obtain a copy of a newly enacted law, they will most likely be looking for the "slip law." A slip law is the first official publication of a public or private law, prepared by the Office of the Federal Register (OFR), and published by the Government Publishing Office (GPO). Slip laws are available from non-commercial, public sources in various forms. Slip laws in printable pamphlet form can be obtained online from GPO. GPO provides free electronic access to official federal government publications, including public and private laws from the 104 th Congress (1995-1996) forward. Additionally, Federal Depository Libraries, which are libraries designated to receive free government documents, provide no-cost access to certain classes of government documents, including slip laws. Public and private laws can also be found through the Library of Congress at Congress.gov, the official website for U.S. federal legislative information. Information on public and private laws may be searched from the 93 rd Congress (1973-1974) forward. The full text of the laws is available beginning with the 101 st Congress (1989-1990). In addition to the publicly available resources described above, many commercial, subscription-based sources provide access to slip laws as well. Subscriptions to these sources vary from House to Senate and within individual offices. Lexis Advance makes public laws available in the USCS - Public Laws database from 1988 to present. ProQuest Congressional makes public laws available in slip law format from 1988 to present. Westlaw makes public laws available from 1973 to the previous legislative session in the U.S. Public Laws - Historical database, and public laws from the current legislative session in its U.S. Public Laws database. Public laws, from 1973 to present are reprinted in the United States Code Congressional and Administrative News (USCCAN), published by Thomson Reuters. Laws are compiled in slip law format chronologically, along with selected Senate, House, and conference reports associated with the laws, as well as presidential signing statements, proclamations, and executive orders. USCCAN is published both as a bound volume and electronically through a Westlaw subscription. Every two years at the end of a congressional session, slip laws (both public and private laws) are accumulated and published chronologically in a series of volumes entitled the United States Statutes at Large ( Statutes at Large ) . The Statutes at Large also contain concurrent resolutions, reorganization plans, proposed and ratified amendments to the Constitution, and proclamations by the President. Until 1948, treaties and international agreements approved by the Senate were also published in the Statutes at Large. Laws are cited by the Statutes at Large volume and page number (e.g., 125 Stat. 753 refers to page 753 of volume 125 of the Statutes at Large ). The printed edition of the Statutes at Large is "legal evidence of the laws...in all the courts of the United States" and thus researchers may likely refer to this publication when citing a law before a court. GPO provides free, electronic access to the Statutes at Large , 1951-2011. Earlier volumes of the Statutes at Large, from 1789 to 1950, can be found and searched through the Law Library of Congress's Digitized Collection. In addition to the publicly available resources described above, many commercial, subscription-based sources provide access to the Statutes at Large . Subscriptions to these sources vary from House to Senate and within individual offices as well. Hein Online makes available the Statutes at Large from 1789 to present, and can also be searched by chapter or public law number. Lexis Advance makes available a Statutes at Large database which contains all public and private laws from 1789 to present, as well as treaties with foreign nations and Indian tribes beginning in 1776. ProQuest Congressional makes available the Statutes at Large from 1789 to present. Westlaw makes available the Statutes at Large from 1789 to 1972. The United States Code ( U.S. Code or U.S.C.) is the official government codification of all general and permanent laws of the United States. The U.S. Code has its roots in an 1866 law that initiated a project to "revise, simplify, arrange, and consolidate all statutes of the United States, general and permanent in their nature...." This endeavor was not fully realized until 1874, when the Revised Statutes of 1874 became the first official codification of U.S. laws. A second edition making corrections and updates followed in 1878. However, despite numerous efforts to supplement and revise inaccuracies in the Revised Statutes , the publication contained errors. The Revised Statutes were also not updated regularly, making it difficult to know if a particular law had been amended. In 1919, work on a new codification project began, but it was not until 1926 that what is today known as the United States Code came to exist. The U.S. Code has been published by the GPO every six years since its initial publication in 1926. The current edition of the U.S. Code was printed in 2012 and is updated annually with cumulative print supplements. In the U.S. C ode , statutes are grouped by subject matter into 54 titles and five appendices. Each title is organized into chapters and then sections, which is how a particular provision is cited (e.g., 27 U.S.C. SS124 refers to Section 124 of Title 27). Source credits and historical notes at the end of each section provide additional information, including the statutory origin of the provision, its effective date, a brief citation, discussion of any amendments, and cross references to related provisions. It is important to note that generally, the U.S. Code is an unofficial restatement of the Statutes at Large organized by topic for ease of access. As discussed further below, the exception to this general rule is when a particular title of the U.S. Code has been enacted into positive law. The Office of the Law Revision Counsel (OLRC) of the U.S. House of Representatives is responsible for maintaining and publishing the U.S. Code . The OLRC oversees the organization of statutes by subject matter, assigning a statute to a U.S. Code section if the law has general applicability and permanence. If a provision is not intended to be permanent or does not have relevance to a wide audience, the OLRC may not include that language in the U.S. Code, or the OLRC may classify the provision as a statutory note or appendix to an existing U.S. Code section. Language enacted as part of government appropriations measures is a common instance of this; for example, provisions appropriating funds to the Office of Highway Administration each fiscal year are not likely to be codified because, by their own terms, they govern for only one year. Nevertheless, it is important to remember that whether a provision is codified or classified as a note or appendix in no way diminishes the statute's significance or authority. Provisions that are not codified in the U.S. Code are still acts of Congress. The language of a law as set forth in the U.S. Code is not necessarily a literal duplication of the law as it was enacted. Because the U.S. Code is arranged by subject, a slip law is often divided up among titles, with different sections of a slip law being assigned to different volumes, chapters and sections of the U.S. Code . There may also be slight changes from the original statute, particularly with regard to section numbers and cross-references, corresponding to U.S. Code sections, not statute sections. The most notable difference between the U.S. Code and the Statutes at Large , however, is that language in the U.S. Code exists as amended to reflect subsequent changes made by later laws. When a bill becomes a law, the OLRC will examine whether the law has any non-amendatory or "freestanding" provisions to introduce to the Code, or any language that revises, repeals, or adds to already existing statutes. Consider the following sequence of enactments. In 1952, Congress passed the Immigration and Nationality Act (INA). The INA generally consolidated and amended federal statutory law on the admission and removal of aliens in the United States and the terms under which they may become U.S. citizens. The INA was codified at 8 U.S.C . SSSS1 et seq. In 1986, Congress passed the Immigration Reform and Control Act (IRCA). Section 101 of IRCA amended the INA by adding new SS274A to the statute. The amendment to the INA is reflected in 8 U.S.C. SS1324a, which was added in 1986. The amending action can be seen in the historical notes of 8 U.S.C. SS1324a, which read: "June 27, 1952, ch. 477, Title II, Ch. 8, SS274A, as added Nov. 6, 1986, P.L. 99-603 [...]." The "as added" segment indicates that SS274A did not originate in 1952, but was added to the INA on November 6, 1986. In 1996, Congress passed the Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA). Section 412 of IIRIRA amended SS274A of the INA. Section 412 of IIRIRA specifically amended 8 U.S.C . SS1324a(b)(1), by striking certain clauses, adding new language, and inserting additional subparagraphs to the existing statute. As the above sequence illustrates, the canvas upon which Congress typically works is the existing realm of federal statutes, and not a blank slate. To that end, it is usually more effective to consult the U.S. Code for the current language of a statute than it is to consult either the slip law or the Statutes at Large , both of which are essentially frozen in their respective times. It can be difficult for a researcher to find amended public laws with up-to-date language, but there are resources available. The House of Representatives' Office of the Legislative Counsel assembles compilations of statutes that are not codified in the U.S. Code or are found in a title that has not been enacted into positive law. Congressional committees and federal agencies may periodically issue similar compilations of amended public laws, especially for statutes significant to their respective jurisdictions. For example, the Civil Rights Division of the Department of Justice provides access to the Americans with Disabilities Act of 1990, As Amended, which includes changes made by the ADA Amendments Act of 2008 to the 1990 law. Additionally, commercial publishers may track changes to existing law by recently enacted legislation. For instance, the commercial database CQ LawTrack notes and lists changes made by each new law to prior laws, though it does not aggregate the text of the amended law itself. In 1947, Congress began enacting whole titles of the U.S. Code into law, generally repealing the underlying statutes. When Congress does this, the authoritative legal language is no longer the slip law that enacted it, but the language as presented in a U.S. Code title. This process is known as "positive law codification" and the titles that have been enacted are "positive law titles." Why would Congress go through the effort of reenacting laws already in force? According to the OLRC, the U.S. Code is an effective and valuable tool for researching and verifying general and permanent laws, and "positive law codification improves the usefulness of the Code in a number of significant ways." These include improving the organization of a title; restating laws using consistent language and styles; eliminating obsolete provisions; resolving ambiguous language; correcting technical errors; and establishing titles as legal evidence of the law so that they are more authoritative in federal and state courts than the Statutes at Large . Non-positive law titles are considered prima facie evidence of the Statutes at Large and may be refuted by the underlying statute should there be a disparity between the two statutes. The process of positive law codification is a meticulous and time-consuming endeavor; consequently, not all titles have undergone the process. At present there are 27 positive law titles, which are identified with an asterisk on the OLRC's U.S. Code "Search & Browse" page. For a researcher, one of the most obvious differences between positive and non-positive law titles is the difference in the history of the enacting laws. In non-positive law titles, the first act listed in the history source credits is what the OLRC terms the "base law," or the act that originated that particular U.S. Code section. For example, 2 U.S.C. SS1 reads, Time for election of Senators . At the regular election held in any State next preceding the expiration of the term for which any Senator was elected to represent such State in Congress, at which election a Representative to Congress is regularly by law to be chosen, a United States Senator from said State shall be elected by the people thereof for the term commencing on the 3d day of January next thereafter. (June 4, 1914, ch. 103, SS1, 38 Stat. 384; June 5, 1934, ch. 390, SS3, 48 Stat. 879.) The base law for 2 U.S.C. SS1 is the Act of June 4, 1914, ch. 103, 38 Stat. 384. In other words, the Act of June 4, 1914 created the language that currently occupies 2 U.S.C. SS1. The opening clause of the Act of June 4, 1914 reads, "An act Providing a temporary method of conducting the nomination and election of United States Senators." However, in positive law titles, the history source credits convey different information. For example, 3 U.S.C. SS7 reads: Meeting and vote of electors . The electors of President and Vice President of each State shall meet and give their votes on the first Monday after the second Wednesday in December next following their appointment at such place in each State as the legislature of such State shall direct. (June 25, 1948, ch. 644, 62 Stat. 673.) Here, the Act of June 25, 1948, ch. 644, 62 Stat. 673 is not the base law for 3 U.S.C. SS7, because this Act did not create the language of Section 7. Rather, this Act codified and enacted the entirety of Title 3 into positive law. The opening clause of this Act reads, "An Act To codify and enact into law Title 3 of the United States Code, entitled 'The President.'" In other words, every section contained in Title 3 has "Act of June 25, 1948, ch. 644" as the enacting law in the source credits because the underlying statutes that individually created the whole of Title 3 have been repealed. Accordingly, for a researcher who needs to cite the authoritative language of a section, the words of the section itself will be sufficient. However, a researcher who is looking for the history of the language itself and is perhaps interested in the intent behind its enactment, must take additional steps to locate such information. A researcher seeking information on the history or intent of the language in positive law titles of the U.S. Code should examine the "Front Matter" located at the very beginning of the title, preceding the legal language. This preface includes a table showing the disposition of all sections of the former title, including where the new sections were previously located, and the original source credits. In the previous example, prior to the process of positive law codification, the language of 3 U.S.C. SS7 was located at 3 U.S.C. SS5, and the original base law was the Act of February 3, 1887, ch. 90, 24 Stat. 373. As discussed in the previous section, one reason for positive law codification is to improve the organization of existing titles. Another way the OLRC improves the organization of existing titles is through a process known as "Editorial Reclassification." In this process, the OLRC reorganizes portions of the law without altering or eliminating any statutory text. The OLRC recently conducted seven editorial reclassification projects. Each one is explained in detail on the OLRC's website, with reasons for the change, major actions, current status, and resources for the transition. As an example, the OLRC transferred Title IV, Part C of the Higher Education Act of 1965 from its current location in the Public Health and Welfare Title, 42 U.S.C . SSSS2751, et seq., to the Education Title, 20 U.S.C. SSSS1087-51, et seq. In addition, portions of Title 20 are being reordered to conform to the transfer. In addition to the official U.S. Code , researchers may be familiar with such resources as the United States Code Annotated (U.S.C.A.), published by Thomson Reuters, and the United States Code Service (U.S.C.S.), published by LexisNexis. These are privately published editions of the U.S. Code . In addition to the text and historical source credits, such editions include annotations with further historical commentary, cross references to the Code of Federal Regulations (C.F.R.), judicial decisions or attorney general opinions interpreting the sections, and citations to secondary sources, such as law reviews and practice guides. Although these supplements can offer benefits to the researcher, it is important to remember that these versions are unofficial and should be cross-referenced to an official publication, be it the slip law, Statutes at Large, or, in the case of a positive law title, the U.S. Code. As previously noted, statutes are incorporated into U.S. Code to facilitate retrieval and access, because searching by subject may be easier than searching by date in some cases. However, there are a number of resources that further simplify locating information in the U.S. Code . The tools listed below are available in both print and electronically via the OLRC, unless otherwise noted. The General Index is a comprehensive directory organized alphabetically by subject with the corresponding title and section listed. The General Index is only available in print format. The Popular Names Table lists statutes alphabetically by their colloquial names. This can reflect the substance of the law, the sponsor(s) of the law, or any creative acronym for the law. For example, there are entries for the "Energy Policy Act," the "Dodd-Frank Wall Street Reform and Consumer Protection Act," and the "USA PATRIOT Act." The electronic version of the Popular Names Table provides the enacting public law number, Statutes at Large cite, and the U.S. Code citation. The Popular Names Table's print version published by Thomson West with the U.S.C.A. also lists all the amending laws under the enacting law. The Classification Tables aid researchers by indicating where enacted laws appear in the U.S. Code and which sections of the U.S. Code those laws amended. The tables will also indicate which sections of the U.S. Code were repealed, omitted, or transferred. Table I conveys where sections of titles enacted as positive law were incorporated into the revised title. If a section is not listed in Table I, then it was either repealed or omitted in the process of becoming positive law. Table II shows where sections of the Revised Statutes of 1878 were classified into the U.S. Code . If a researcher has a Statutes at Large cite and would like to know where it has been codified, Table III provides the corresponding U.S. Code section. Similarly, Tables IV and V indicate where a particular executive order or presidential proclamation is set out in the U.S. Code . Likewise, Table VI lists the codification and status of reorganization plans promulgated since 1939. A reorganization plan is a proposal offered by the President to restructure or modify existing federal agencies to improve efficiency by consolidating, transferring, or eliminating certain functions. For additional information or specific questions on federal statutes, congressional clients may contact CRS. For programs offering training on statutory research, congressional clients please consult "Federal Legal Research" under the "Events" section of CRS.gov.

Summary:
This report provides an overview of federal statutes in their various forms, as well as basic guidance for congressional staff interested in researching statutes. When a bill becomes a law, the newly enacted statute may amend or repeal earlier statutes or it may create a new or "freestanding" law. Either way, these new statutes are first printed individually as "slip laws" and numbered by order of passage as either public laws, or less frequently, private laws. Slip laws are later aggregated and published chronologically in volumes known as the United States Statutes at Large (Statutes at Large). Statutes of a general and permanent nature are then incorporated into the United States Code (U.S. Code), which arranges the statutes by subject matter into 54 titles and five appendices. Statutes may be updated and published as amended public laws. As the statutes that underlie the U.S. Code are revised, superseded, or repealed, the provisions of the U.S. Code are also updated to reflect these changes. In these instances, the authoritative language remains the enacting statute, or the "base law." However, some titles of the U.S. Code have been passed into "positive law," meaning the law exists as it does in the U.S. Code and the title itself is the authoritative language. In these instances, it is the U.S. Code sections that are revised, superseded, or repealed, as the underlying statutes have all been revoked. In arranging statutes by subject rather than date, the U.S. Code may be more convenient to search than the Statutes at Large. Moreover, the Office of the Law Revision Counsel publishes tools known as "Tables," to assist researchers in locating statutes, as well identifying statutes that may have been amended, omitted, transferred, or repealed. Nevertheless, certain laws are not added to the U.S. Code, such as laws appropriating funds, and thus researchers will often need to search laws in the other forms discussed herein.