Guide last updated by Tiffany Souza and David Percik, July 2023
We also recommend the following online research guides for foreign jurisdictions.
The United States has a common law federal legal system in which the written Constitution allocates particular powers to the federal government leaving the remainder to the individual states. The federal and 50 individual state governments operate in parallel, all with their own executive, legislative and judicial branches. As a consequence there is a large body of primary law covering the federal and state systems.
IALS has an extensive collection of U.S. Federal primary and secondary resources in print and electronic formats and a more selective collection of State primary resources, concentrating on California, Louisiana, New York, Pennsylvania, and Texas.
Legislation at both the federal and state levels is hierarchical, with the constitution at the top and statutes and regulations below. Statutes and regulations are published both chronologically and in codified form.
The U.S. Constitution, “the supreme Law of the Land”, defines the structure of the federal government with the separation of powers between the legislative, executive and judicial branches, defines the powers of the federal government and guarantees the basic rights of U.S. citizens, such as the right to "bear arms".
The U.S. Constitution is arranged in (roman) numbered Articles, which are subdivided into Sections and then into Clauses. An example of a citation would be: U.S CONST. Art. II, §1, cl. 7. Amendments appear separately at the end.
Each of the 50 states also has a constitution, which establishes the structure of state government and guarantees fundamental rights. State constitutions vary considerably in length and scope. They cannot deprive persons of federal constitutional rights, but they can guarantee additional protections not found in federal law.
The U.S. Constitution is available from numerous electronic sources, and a useful list is produced by the Library of Congress.
In particular it is worth noting:
The Constitution of the United States published on the US Government Printing Office site.
The Constitution as exhibited on the National Archives website
Findlaw has a copy with annotations.
The text is available on both Lexis (database ID USCS) and Westlaw (database ID USCA-CONST). See our Westlaw and Lexis Guides for more information. It is also available on World Constitutions Illustrated (HeinOnline).
State constitutions are freely available online on states’ websites and websites providing multistate access. One useful resource is Oxford Constitutions of the World.
The main and official printed source for the U.S. Constitution is the United States Code. IALS has the annotated code at classmark GP1.E.9.
Federal statutes (both public and private) are published chronologically first as slip law pamphlets and later as session laws in the United States Statutes at Large. Public laws of a “general and permanent” nature are subsequently codified in the United States Code. Commercial entities then create annotated versions of the U.S. Code. These are often the best place to start statutory research because they include case citations. West has the United States Code Annotated (U.S.C.A.); Lexis has the United States Code Service (U.S.C.S.).
Federal statutes: chronological
Public laws are cited by title and date as in the UK. Since 1957, the numeric citation has been in the form Pub. L. 102-61 where 102 means that the law was passed by the 102nd Congress, and 61 means that the law was the 61st law passed during that Congress. A Congress lasts for two annual sessions. (The 102nd Congress was from January 1993 to December 1994). Joint resolutions of the House and Senate are numbered as Public Laws.
Private laws are published only in the Statutes at Large series. Citation is in the form: Priv. L. 102-29.
Example of a reference for a specific section of an Act:
National Environmental Policy Act of 1969, Pub. L. 91-190, § 102, 83 Stat. 852 (1970).
The GPO site (Govinfo) has the official version of Public and Private Laws from the 104th Congress (1995-96) to date. PDFs of Statutes at Large are available there from the 82nd Congress (1951-52). Earlier volumes are available from the Library of Congress.
HeinOnline has them from 1789 to date.
Lexis has the Statutes at Large.
Westlaw has a much shorter file of Public Laws in two parts: US-PL for the current term and US-PL-OLD for the period 1973 to (the previous term). Westlaw also has an online version of the Congressional & Administrative News: database ID: USCCAN. (includes US-PL, US-PL-OLD for the dates mentioned, plus LH, the legislative history materials back to 1948).
The official series of chronologically published laws is the Statutes at Large, which is analogous to the British Public General Acts series. It is held in the IALS basement at RES FOL GP1.E.14 up to 1942 and is also available in LSE and the British Library (from 1975). Citation is by volume and page in the form 89 Stat. 213.
IALS also has the Congressional & Administrative News, published by West from 1941 (the IALS set is complete except for 1941), shelved at GP1.E.12. It includes an extensive selection of "legislative history", including items such as House or Senate committee reports produced during consideration of a bill. Starting with 1975, the pagination conforms to that of the Statutes at Large.
Federal statutes: codes
Codification is the process by which statutes are rearranged into subject order and any subsequent amendments are incorporated. This does not mean that the U.S. has a "Napoleonic code" legal system such as is found in civil law jurisdictions, (although the state of Louisiana is the exception, like Quebec in Canada, in that it does have a system of private law based on the French Code Civil).
When looking for a statute in the U.S. Code, it is important to be aware that a statute could have its sections “scattered” through a number of different titles within the U.S. Code, and some Acts are not codified at all. If the Act dates from before Congressional & Administrative News (start date 1941, IALS copy 1942), use Statutes at Large.
Lexis has the United States Code Service (U.S.C.S.), which is the online version of an annotated paper edition published by Michie in over 200 volumes. Use “Find Source” and enter “united states code”. To reach title 42 section 4332 for example, use cite 42 & 4332 as your search.
Westlaw has the code in Database ID: United States Code Annotated (U.S.C.A.) (But use Find by Citation if you can).
HeinOnline has several editions of the United States Code, from 1925 to 2006.
The official compilation is the United States Code (official edition). The subtitle reads: "Containing the General and Permanent Laws of the United States, in force on January..." It is published every 6 years by the U.S. Government Printing Office, and updated by bound annual cumulative supplements.
It is arranged in 50 numbered, alphabetically arranged "Titles" covering broad subjects. For example, Title 15 is Commerce & Trade; Title 42 is Public Health & Welfare. The U.S. Constitution is included, but outside the numbered Title sequence. Within each Title the sections are numbered in a single long sequence. Citation is in the form 18 U.S.C. §1206. It should be noted that the section numbers in U.S.C. do not relate to the section numbers in the original legislation. However, the original section numbers are still the official way to cite, even though your main source for an updated version is the U.S. Code.
Example of a full reference to a specific section of an Act as currently in force: National Environmental Policy Act of 1969 § 102, 42 U.S.C. § 4332 (2000).
The IALS set of the official edition is out of date, being a mixture of the 1982 and 1988 editions / supplements), and is shelved in the closed basement. The British Library has the "2000 edition" (laws in force on January 2, 2001); it should also be at LSE.
The IALS holds the commercially published United States Code Annotated (West) shelved at classmark GP1.E.9, but this is only up-to-date to 2010. This has a large amount of annotation, including case digests and law review articles related to each section. The set was updated, until 2010, by annual pocket parts in the back of the volumes, plus quarterly pamphlets. For citation, West Publications use the style 42 U.S.C.A. § 4332.
Finding statutes: electronic
Lexis and Westlaw have online versions of the Popular Name Table. Westlaw, unlike Lexis, lets you enter a citation. Use the “Find by Citation” tab, make sure you change the country to US - United States then enter e.g., 13 usc 1300 or pl 94-123.
Finding statutes: print
For statutes up to 2010, you can use the Tables volumes or General Index (if you are searching for a statute by subject) in U.S.C.A. (or U.S. Code).
For later statutes, it is best to search U.S.C.A., which is available on Westlaw.
Finding cases which refer to statutes
Use the case annotations in U.S.C.A. on Westlaw, but note that section references might be to the U.S. Code version, not the original Act.
Federal regulations: chronological
The executive branch of the U.S. government generates a large amount of regulatory material, including regulations (rules) made by departments and agencies of the federal government (equivalent to British Statutory Instruments) and Presidential Proclamations and Executive Orders (approximately equivalent to Orders in Council).
The Federal Register is where regulations, notices and other documents (including proposed rules) are published on a daily basis. Each volume covers one calendar year. Pagination is continuous within each volume and has exceeded 60,000 pages per year since 1991.
In addition, individual agency websites include links to relevant regulations, reports, guidance documents and enforcement actions.
The Federal Register is available free on the Federal Register website.
HeinOnLine has the Federal Register in PDF format from vol.1 (1936) onwards.
Lexis has it from 1980 onwards. Use Find Source and enter “federal register”.
The Westlaw Database ID is FR with a start date of 1980.
The official printed source is the Federal Register 1936- . This is not held in IALS but is in the British Library and LSE Library. Regulations are also printed in the Congressional and Administrative News, which is in IALS and shelved at classmark GP1.E.12.
Federal regulations: codes
The Code of Federal Regulations (CFR) is on the GPO website and on the Cornell Legal Information Institute website. For the most current information, use the eCFR, which is continuously updated but is not the official edition of the CFR.
The CFR is also on HeinOnline for the years 1938 - date.
On Lexis, use Find Source and enter “federal regulations”.
On Westlaw, the Database ID is CFR. The numbering is tricky, so a “Find by Citation” search may fail.
These follow a similar publication pattern to federal statutes: in practice codified versions are normally used in preference to session laws.
Lexis and Westlaw also have this material.
IALS currently subscribes to the codes (not session laws) from the state of Louisiana (civil, civil procedure, criminal procedure).
Uniform laws are devised by the National Conference of Commissioners on Uniform State Laws (now generally known as the Uniform Law Commission), which was formed in 1892 to promote state enactment of uniform laws to reduce the confusion caused by conflicting state statutes. States can adopt uniform laws as proposed, modify them, or ignore them. Over 300 uniform laws have been approved by the Uniform Law Commission, and more than half have been adopted by at least one U.S. state. The prime example is the Uniform Commercial Code, which has been adopted in some form by all 50 states.
Sources of Uniform laws
The main printed source is the set of volumes titled Uniform Laws Annotated (West Publishing). IALS holds these at classmark GP1.E.8. This series contains all the uniform laws which have been adopted by at least one state and includes references to variations in individual states.
Electronic versions of uniform laws are freely available on the Uniform Law Commission website, which also shows which states have adopted the laws, monitors legislative activity, and includes links to PDFs of enacted state laws.
Lexis contains the Martindale-Hubbell uniform and model acts which offer a selection of uniform laws and parts of the Uniform Commercial Code.
Westlaw Database ID: ULA.
The U.S. has both federal and state courts, and it depends on the nature of the case and other factors as to which court will have jurisdiction. Note that federal courts do not sit just in Washington, DC; there are federal courts in the states as well.
Conflict of laws is an important issue in the U.S. involving matters such as the choice of law as between states and the choice of forum (venue).
The citation style is the same as in the UK, except that the date is usually given at the end. For example, here is a U.S. Supreme Court case citation: 496 U.S. 226 (1990).
Published federal and state court decisions are available from several sources (detailed below). In addition, Harvard Law School has digitised all official, book-published state and federal United States case law (every volume or case designated as an official report of decisions by a court within the United States since 1658) in its freely available Caselaw Access Project.
The main federal courts of general jurisdiction are the U.S. Supreme Court, the U.S. Courts of Appeals (in 12 regional circuits plus 1 Federal) and the U.S. District Courts (in 94 judicial districts).
(a) Supreme Court cases
The Supreme Court website has PDF versions of decisions starting with vol. 502 U.S (October 1991 term).
HeinOnline has a PDF archive of the U.S. Reports from 1754 (vol.1) to 2015 (vol.582).
Lexis has the L. Ed. version from 1790 onwards. Use Find Source and search on supreme court. Select "U.S. Supreme Court Cases, Lawyers' Edition" from the list, avoiding the sub-sets.
On Westlaw, as with statutes, you can find a case directly by its citation, or if searching by terms use the file name SCT for cases after 1944, and SCT-OLD for cases between 1790 and 1945.
Supreme Court cases are published in three printed series of which IALS holds one:
Note: the volume and page numbering for the L. Ed. version is not the same as the official U.S. Reports, but the U.S. numbering appears on the spine of the L. Ed. volumes in smaller print.
Until 1874, it was usual to cite by the name of the reporter (similar to the UK nominate reports), but then "U.S." volume numbers were assigned retrospectively, so that e.g., 12 Wheat. = 25 U.S., and 23 Wall. = 90 U.S.
(b) Lower Federal Courts
(i) Courts of Appeals
Precedential decisions of the U.S. Courts of Appeals are published in the Federal Reporter shelved in IALS at classmark GP1.G.12 (some of it is in the basement with classmark prefix RES). They are cited F. (or F. 2d, or F. 3d for the second and third series).
(ii) District Courts
Few District Court decisions are published in West’s National Reporter System. Selected cases were published in the Federal Reporter up to 1932 and since then have been published in the Federal Supplement at classmark GP1.G.7. (Some of it is in the basement with classmark prefix RES). They are cited F. Supp. (or F. Supp. 2d for the second series).
Lexis and Westlaw have the most comprehensive coverage of federal court decisions and include cases that are not published in the National Reporter System.
Although every federal court has its own website with links to decisions, coverage is not complete. Links to these websites are available on the U.S. Courts website.
Govinfo.gov has a United States Courts Opinions collection, which includes decisions back to the early 2000s from all Courts of Appeals and some District Courts and Bankruptcy Courts, but coverage varies.
Harvard Law School’s Caselaw Access Project provides free access to digitised copies of all book-published federal cases.
Each U.S. state has its own court system, with a state supreme court at the top of the hierarchy. State official reports are the authoritative version of the state’s court decisions. Most states have their own official reports; some states have designated the West reporter as the authoritative source of state case law. West publishes a number of regional law reporters which report the highest court decisions from each state in the region covered by the reporter. Start dates are all in the 1880s, and each regional reporter is now in at least a second series.
Citations for state reports not held in IALS can be translated into citations to the various National Reporter series which are in IALS using the National Reporter bluebooks. These are shelved at classmark GP1.G.114.
Harvard Law School’s Caselaw Access Project provides free access to digitised copies of all book-published state cases.
Some state court decisions are also available on both Lexis and Westlaw.
IALS does not currently subscribe to any of the individual state series in print (it does hold some old series), but the Library has all the regional units of West's National Reporter System: Atlantic, North Eastern, North Western, Pacific, South Eastern, Southern, and South Western Reporter, up to early 2008. All first series and the first 100 volumes of each second series are in the offsite store or in the basement. California Reporter from 1959 onwards and now in its 3rd series (at IALS classmark GP5.G.2) and New York Supplement now in its 2nd series (at IALS classmark GP31.G.7) include some lower court decisions not reported in the Pacific and North Eastern Reporters respectively.
Decisions of the District of Columbia Court of Appeals are included in West’s Atlantic Reporter with state court cases.
Decisions of the appellate courts of the U.S. territories Guam, Northern Mariana Islands, Puerto Rico, and the Virgin Islands are not included in West’s National Reporter System. These decisions may be found in official reports or online through the court’s website or on Lexis or Westlaw.
Decisions of tribal courts can be difficult to find as there are no published decisions for the majority of federally recognized tribes in the United States. Some decisions are available on Lexis and Westlaw. The Indian Law Reporter (1974 – 2013) is available on HeinOnline. The Tribal Court Clearinghouse website has links to tribal websites that post some court opinions.
American Law Reports (ALR)
This is an important series of law reports which is often regarded as a journal. It has been published since 1919 and is shelved in IALS at classmark GP1.G.10 for the 3rd to 5th series. The first and second series are in the basement with classmark prefix RES. The series contains selective reports of appellate cases, but its most important feature is that it also contains lengthy encyclopaedic essays or "annotations" that provide comprehensive summaries of the case law on specific topics. The series is often cited in the literature for these annotations. From the 5th series onwards, the case reports are at the end of the volume after the annotations, and form a quite small proportion of the content.
Since 1969, federal appellate cases have been published in ALR Federal shelved at IALS classmark GP1.G.34. All the ALR series have their own indexes and updating volumes.
ALR annotations (1919 – date) are available on Westlaw. Lexis has ALR annotations (1948 – date) and the Lawyers’ Edition annotations focusing on Supreme Court cases. Annotations are updated annually and are considered secondary sources.
Currency of print U.S. law reports at IALS
With the exception of the Supreme Court reports, IALS no longer subscribes to the print Reporter series. Therefore IALS print holdings will not contain recent cases. For Supreme Court decisions, IALS receives the advance paper parts and interim bound volumes as well as the permanent bound volumes which are about 5 years behind in publication. Until 2009, IALS subscribed to US Law Week which provides information on new cases. Otherwise it is necessary to use electronic sources. The Supreme Court website has recent slip opinions. Academic users can use Lexis+ or Westlaw.
IALS no longer subscribes to any major US "narrative" encyclopaedic digests (like Halsbury's Laws) in print. It holds historic sets of:
Case law is referential. Cases decided today will cite earlier cases, and cases decided in the future may rely on cases decided today. Specialised research tools called citators help keep track of citation networks by locating other relevant legal authorities (e.g., cases that cite your case) and determining the validity of your case. Because citators link cases by shared issues, they provide one of the most effective ways to find sources for further research.
Most citator research occurs online using Lexis or Westlaw. Lexis has Shepard’s Citations, and Westlaw has Westlaw Citing References (also known as KeyCite).
Citation analysis was formerly done with print versions of Shepard’s Citations and West KeyCite. The system was completely different from the British equivalent and consisted of numerical tables arranged by source citation. As an example: if you had a case reported at 263 S.E. 2d 391, you looked up that citation in the Shepards South Eastern Reporter Citations volume and found a column of the citations for cases which had considered your case. Various superscript codes indicated what treatment was given by the citing case (followed, distinguished etc.).
IALS only holds historic Shepard’s print sets up to 1994 relating to the law reporter series we subscribed to.
The closest to the British style "Encyclopaedia of... law" (i.e., a mixture of statutes, cases, official circulars etc.) are probably the CCH "Reporters" which are published commercially in looseleaf. IALS has a few of these, but has largely discontinued the subscriptions.
Black's Law Dictionary 11th ed., 2019. Shelved at RF72 BLA is a one-volume standard work.
Fox, E.H. The Legal research dictionary: from advance sheets to pocket parts 2nd ed. 2006. (Useful for brief definitions of types of publications)
Words & Phrases 1658 to date (at GP1.H.16) "All judicial constructions and definitions of words and phrases by the state and federal courts from the earliest times, alphabetically arranged and indexed". Over 90 volumes!
Restatements of the Law attempt to articulate the basic doctrines governing American law in specific subject areas. They are "[a]n attempt made by the American Law Institute to have formulated in propositions, rather like the articles of a code, what are deemed to be the best doctrines and principles of the main branches of the law of the U.S., particularly the branches still mainly dependent on case-law". (Walker, D.M. The Oxford Companion to Law, 1980).
The Restatements are prepared by academics, judges and practitioners in a variety of subjects including agency, contracts, foreign relations law, restitution, torts, trusts and conflict of laws. Many are in 2d or even 3d editions. They contain rules and commentary, and are perhaps more persuasive in the courts than any other secondary material.
IALS has a complete set in print, and they are all available on Westlaw, Lexis and HeinOnline.
IALS holds some print bibliographies:
U.S. law school library catalogues can be a useful source of current information (e.g., Columbia, Georgetown, New York University, Yale).
The literature is too vast to collect everything, particularly with material on both federal and state law available. In general, IALS tries to stock at least one major work in the main subject areas. Many are multi-volume works in looseleaf or are updated annually with pocket parts, such as:
Most deal primarily with federal law, but IALS does collect some important state material (e.g., Balotti & Finkelstein, The Delaware law of corporations and business organizations).
Details of U.S. government publications from 1976 onwards are available on the U.S. Government Printing Office website. For older material, there is the Monthly catalog of US government publications. IALS has online access up to the end of 2004 through LLMC Digital.
IALS has very few U.S. government publications. The LSE Library is a depository library for U.S. government publications and so has a large collection of these materials.
In addition, most current and historic U.S. government publications are available online. Links to the key sources of U.S. government information online are available on LSE Library’s website.
The IALS Library has a very extensive, though not comprehensive, collection of American law journals, comprising over 500 titles. Generally speaking IALS does not subscribe to titles aimed purely at the practitioner, such as newsletters issued by the various sections of the American Bar Association. Some titles, or early volumes in a title, may be shelved in the offsite store or in the closed basement. For details consult the online catalogue.
Many titles, including those published by the American Bar Association, are available electronically in HeinOnline, Lexis and Westlaw.
IALS holds or provides access to several major journal indexing services.
Index to Legal Periodicals is available electronically from 1981.
On Lexis, use Find Source and enter Index to legal periodicals.
On Westlaw, the easiest access is direct by database ID: either ILP or LRI.
Martindale-Hubbell Law Directory. This is produced annually and is considered the main source, although it does not have any official status, and lawyers pay to get an entry. IALS does not have a current print subscription, but the main directory information is available free on the Martindale-Hubbell Law Directory website. The online version does not include the very useful foreign law digests, which are part of the printed set.
The Bluebook: a uniform system of citation. 21st ed., 2020.
It is compiled by the editors of the Columbia Law Review, the Harvard Law Review, the University of Pennsylvania Law Review, and the Yale Law Journal.
IALS has The Bluebook (20th ed.) in print at classmark RF73 UNI. The Bluebook is also available in an online version, but access requires a paid subscription.
Barkan, S., Bintliff, B & Whisner, M., Fundamentals of legal research, 10th ed. Foundation Press, 2015.
Cohen, M & Olson, K., Legal research in a nutshell, 10th ed., West, 2010.
Lomio, J., Spang-Hanssen, H. & Wilson, G., Legal research methods in a modern world, DJOF Publishing, 2011.
Manz, W., Gibson’s New York legal research guide, 4th ed., Hein, 2014.
Neacsu, D., Introduction to US law and legal research, Transnational Publishers, c2005.
Olson, K., Principles of legal research, 2nd ed., West Academic Publishing, 2015.
U.S. law school library research guides provide links to free electronic sources of U.S. law. For example:
Here are some additional websites that offer free access:
GPO access https://www.gpo.gov/
Hieros Gamos http://www.hg.org/
Eagle-i Internet Portal for Law https://resources.ials.sas.ac.uk/eagle-i/search
These 2 subscription databases are only available at IALS to academic researchers. For information about who can access these databases and how, see the IALS Law Databases list.
Both Lexis+ and Westlaw UK provide access to U.S. materials for UK users, but both launch with a British based front screen and you must select the appropriate part to access the international resources.
In Lexis+, click on the Sources tab, choose Browse Sources, and then select United States from the country filter.
In Westlaw, to select Federal, click Services on the toolbar, then click Westlaw International, and select US Federal. For state materials either use the “law school classic” tab or click on “Directory” at the top of the screen then select “All Westlaw databases”. Westlaw provides a very useful “Find by Citation” function which works on the U.S. primary sources, though not so well on the journals.