Wikipedia:Identifying reliable sources (law)

Information about the law should be based on reliable, third-party published secondary sources.

Law sources such as books about laws and articles about laws in magazines and academic journals may be reliable sources. Whether a law source is reliable or not needs to be assessed separately for each source. Law sources that are written by authoritative experts in law, such as legal scholars, and published by respected independent publishing houses are normally reliable sources. General information about laws that is provided on websites for the general public or which appears in general interest magazines such as Reader's Digest is often written by non-lawyers, and editors will have to determine in each case if the source is reliable. This essay is based on U.S. law, both federal and non-federal. This applies whether the subject is the U.S. Constitution or a lower-level agency branch office manual that nonetheless has the force of law, or something in between.

For guidance on how to properly format legal sources, see Manual of Style/Legal.

Law itself or effect of law
Some sources attempt mainly to state what the law itself says. Some other sources attempt to state the effect of the law, such as a source about social effects or impacts arising from the implementation of a law, a source about a policy recommendation that in someone's opinion should be embodied in a law, a source about the legislative process, or a source on constitutional history. This essay is about sources that attempt mainly to state the law itself, and not about sources that attempt mainly to state the effects or impacts of the law.

Lay vs. professional readerships
Law sources are written for either of two audiences, with little overlap:
 * Lay audiences who do not understand much law. These include business managers and owners, journalists, junior high school students, and many people employed in non-legal fields. What these audiences share is that they have not had the kind of legal training that law schools provide. They may know their most important legal rights and obligations, but they probably don't understand how lawyers communicate with each other and with judges.
 * Professional audiences, usually lawyers, judges, legal scholars, and law students.

The differences are consequential for content:
 * Lay law sources don't usually distinguish among states and other non-Federal jurisdictions for legal differences. Lay law sources do not detail most of the finer points of law, or explain procedures that lawyers usually are in charge of handling, such as court adjudication. But they are easier for lay people to read. Some are written by lawyers and some are by lay writers. Government agencies may have non-lawyers write on law. Some lay writers can be imprecise, so it's important to judge the reliability of each source.
 * Professional law sources don't usually explain legal concepts or definitions that lawyers or judges would know anyway or detail interactions with other subjects of law; and they tend to be heavily footnoted, and lay readers often find them intimidating. But they are more precise about the law they do cover. Almost all are authored by lawyers and law professors.

Old vs. new
After a year (more or less), secondary sources tend to become less reliable or unreliable except as history. The one-year point in time is arbitrary, since any subject of law can change at any time in a vital way and some subjects change rapidly in crucial ways, while others may be relatively stable for centuries, but the one-year time is conventionally accepted for many subjects. Some sources that are one-time publications have annual and even quarterly supplements, which should always be checked; these are often found in the back as pocket parts (pamphlets that slip into pockets in books' back covers).

Primary sources are subject to interpretation and interpretations can change anytime. For example, when a court interprets the Constitution, it may not be creating new law even if most people think it is, but discovering the law already there that even most law professors hadn't known before the ruling.

Original texts
Organic laws, constitutions, treaties and other binding international agreements, statutes as enacted, statutes as codified, agency regulations, some agency manuals and similar issuances, court decisions and the majority and some other opinions issued with them, decisions by agency adjudicative bodies, executive orders, presidential proclamations, and certain government orders (such as some military orders, including some verbal ones) are examples of primary sources. Some codified statutes might be considered as secondary if the codification was by someone other than the enacting body or its delegated representative responsible for codifying, but it usually would be more prudent to consider even those as primary sources, because, while codification by the enacting body produces positive law, codification by anyone else may still produce prima facie evidence of the statutes, which makes the source virtually primary. Court opinions are primary for both holdings of law (ratio decidendi) and legal points not necessary to the holdings (obiter dicta); a secondary source about either portion of a court opinion might be a journal article. Annotations in codifications published by nongovernmental companies, when the annotations themselves are by authors who are not in the government, are generally secondary (these are discussed below and generally are descriptions of court rulings). Thus, the same books, even the same pages, often include both primary and secondary sources.

Other primary sources of law include amendments that were proposed but rejected (including constitutional amendments and legislative bills), reports of legislative committees for legislation subsequently enacted, legislative floor debates leading to passage, judicial concurrences and dissents, common law, contracts, and documents issued by one person each, such as wills and, sometimes, letters. Some common law, contracts, and one-person-issued documents are unverifiable and unverifiable sources may not be cited in Wikipedia.

Indian tribes operate within two bodies of law. One is the law of the U.S. that applies to tribes, some of which have limited sovereignty flowing from treaties between tribes and either past colonists or the U.S. government. The other is each tribe's own law, much of it grounded in pre-U.S. tribal law, some of which is based on oral tradition. In Wikipedia, we should not rely on oral tradition unless a source is provided.

Official summaries or syllabi
A court may publish its opinions in a case with a syllabus. A legislature may publish with a bill a summary issued by the legislature or by a legislator who introduced the bill. Because of who authored the syllabus or summary and because the author is likely hired and supervised by the people who authored the court opinions or the bill and because the employee's duty is partly to author the summary or syllabus, the syllabus or summary should be treated as essentially primary, like the court opinions and the body of the bill.

Treatises and law journals
Journal articles and treatises generally are secondary sources and many are excellent. Some are cited approvingly by courts in their majority opinions. None are written mainly for lay audiences; all are written for lawyers and allied professionals.

Casebooks
Legal casebooks are less comprehensive than treatises and journal articles in stating the law. According to Bruce W. Frier and Thomas A.J. McGinn, coauthors of one casebook, "a casebook relies on direct use of primary sources in order to convey a clear understanding of what legal sources are like and how lawyers work." They can be very good in describing the law on a specific point, especially a point for which a case is reprinted, and in indicating the very general nature of the law on the broader subject encompassed by the casebook. But they are not comprehensive guides to the law on any subject that is large enough to depend on multiple primary sources, and generally are not meant to be.

Annotated statutes
Statutes in codified form may include annotations about court rulings. State statutes are often published only this way and Federal statutes are available both ways. The annotations themselves are secondary sources even while the statutes in the same books are virtually primary. The quality of the annotations is often not as high or thorough as are descriptions of the same cases in treatises and journal articles. The annotations are also more stable, not changing after each one is first published, while treatises and casebooks may change with each edition.

Loose-leaf services
Loose-leaf reporters generally combine treatise-like content, original texts, and finding aids, with content often available nowhere else. Treatise-like content should be evaluated in comparison with treatises generally while original texts should be evaluated in comparison with other original texts.

Dictionaries, encyclopedias, restatements, and finding aids
Dictionaries specifically for lawyers are more reliable than dictionaries about law written for lay audiences. Legal encyclopedias, of which only a few exist, tend to be less high in quality than treatises or journal articles; for example, they may limit their content to what courts have said, omitting much analysis of statutes and other codified sources. Restatements may take the form of a treatise or an encyclopedia on one legal subject but may be aspirational, emphasizing what should be the law rather than what is. Finding aids (such as popular name tables), if they're to be used (in rare cases) as direct sources for Wikipedia, are to be evaluated for reliability before use (they may be freely used to aid in your research without being sources in themselves).

Briefs and memoranda
When written by a party to litigation or by a so-called friend of the court (usually an amicus curiae or amicus) or as advice from a lawyer to a client or to another lawyer, a brief or a memorandum is probably a primary source and should be considered as advocacy for one adversary for which balance from an opposing party is needed and even the balance is often insufficient. While they may quote reliable sources, they are not reliable regarding those other sources, because the quoting is itself a form of one-sided advocacy.

News media and broadcasts
News media outside of law, especially newspapers, have been described as providing the first draft of history. That likely applies to news media that specialize in law, too. Reliability varies between general media and legal media, the latter probably being more reliable on average. When time has passed and more stable sources have been published, generally the latter should be used instead of older news media.

Broadcasts are generally for lay audiences and tend to be superficial, even when conducted by practicing attorneys. Perhaps the only exception is the U.S. Supreme Court's unofficial oral argument recordings, which are prepared for major cases in which oral argument was conducted by the parties with the justices present and asking questions, and those recordings are generally primary sources.

Websites and online subscriptions
The same analysis applied to print media should be applied to electronic media, whether to be paid for or free.