The law of the United States comprises many levels of codified and uncodified forms of law, of which the supreme law is the nation's Constitution, which prescribes the foundation of the federal government of the United States, as well as various civil liberties. The Constitution sets out the boundaries of federal law, which consists of acts of Congress,Ex parte Virginia, . treaties ratified by the Senate,Head Money Cases, . regulations promulgated by the executive branch,Skidmore v. Swift & Co., . and case law originating from the federal judiciary.Cooper v. Aaron, . The United States Code is the official compilation and codification of general and permanent federal statutory law.
The Constitution provides that it, as well as federal laws and treaties that are made pursuant to it, preempt conflicting state and territorial laws in the 50 U.S. states and in the territories.William Burnham, Introduction to the Law and Legal System of the United States, 4th ed. (St. Paul, MN: Thomson West, 2006), 41. However, the scope of federal preemption is limited because the scope of federal power is not universal. In the dual sovereignGregory v. Ashcroft, . system of American federalism (actually tripartite because of the presence of Indian reservations), states are the plenary sovereigns, each with their own constitution, while the federal sovereign possesses only the limited supreme authority enumerated in the Constitution.United States v. Lopez, . Indeed, states may grant their citizens broader rights than the federal Constitution as long as they do not infringe on any federal constitutional rights.Pruneyard Shopping Center v. Robins, .California v. Ramos, . Thus U.S. law (especially the actual "living law" of contract, tort, property, probate, criminal and family law, experienced by citizens on a day-to-day basis) consists primarily of state law, which, while sometimes harmonized, can and does vary greatly from one state to the next. Even in areas governed by federal law, state law is often supplemented, rather than preempted.
At both the federal and state levels, with the exception of the legal system of Louisiana, the law of the United States is largely derived from the common law system of English law, which was in force in British America at the time of the American Revolutionary War. Professor Friedman points out that English law itself was never completely uniform across England prior to the 20th century. The result was that the colonists recreated the legal diversity of English law in the American colonies. However, American law has diverged greatly from its English ancestor both in terms of substance and procedure and has incorporated a number of civil law innovations.
General overview
Sources of law In the United States, the law is derived from five sources: constitutional law, statutory law, treaties, administrative regulations, and the common law (which includes case law).
Constitutionality If Congress enacts a statute that conflicts with the Constitution, state or federal courts may rule that law to be unconstitutional and declare it invalid.See Marbury v. Madison, .
Notably, a statute does not automatically disappear merely because it has been found unconstitutional; it may, however, be deleted by a subsequent statute. Many federal and state statutes have remained on the books for decades after they were ruled to be unconstitutional. However, under the principle of stare decisis, a lower court that enforces a statute of a kind previously declared unconstitutional will risk reversal by the Supreme Court.James B. Beam Distilling Co. v. Georgia, Conversely, any court that refuses to enforce a statute previously upheld as constitutional by higher courts risks being reversed by the Supreme Court.See Casarotto v. Lombardi, 886 P.2d 931, 940 (Mont. 1994) (Trieweiler, J., specially concurring), vacated and remanded by 515 U.S. 1129 (1995), reaffirmed and reinstated by 901 P.2d 596 (Mont. 1995), reversed sub nom. Doctor's Assocs., Inc. v. Casarotto, .Cavazos v. Smith, (per curiam).
American common law
The United States and most Commonwealth countries are heirs to the common law legal tradition of English law. Certain practices traditionally allowed under English common law were expressly outlawed by the Constitution, such as bills of attainderU.S. Const., Art. 1, §§ 9 and 10. and general search warrants.U.S. Const., Amend. IV.
As common law courts, U.S. courts have inherited the principle of stare decisis.John C. Dernbach and Cathleen S. Wharton, A Practical Guide to Legal Writing & Legal Method, 2nd ed. (Buffalo: William S. Hein Publishing, 1994), 34–36. American judges, like common law judges elsewhere, not only apply the law, they also make the law, to the extent that their decisions in the cases before them become precedent for decisions in future cases.
The actual substance of English law was formally "received" into the United States in several ways. First, all U.S. states except Louisiana have enacted "reception statutes" which generally state that the common law of England (particularly judge-made law) is the law of the state to the extent that it is not repugnant to domestic law or indigenous conditions.Miles O. Price & Harry Bitner, Effective Legal Research: A Practical Manual of Law Books and Their Use, 3rd ed. (Buffalo: William Hein & Co., 1969), 272. Some reception statutes impose a specific cutoff date for reception, such as the date of a colony's founding, while others are deliberately vague.Ibid. Thus, contemporary U.S. courts often cite pre-Revolution cases when discussing the evolution of an ancient judge-made common law principle into its modern form, such as the heightened duty of care traditionally imposed upon common carriers.See, e.g., Gomez v. Superior Court, 35 Cal. 4th 1125, 29 Cal. Rptr. 3d 352, 113 P.3d 41 (2005) (citing Lovett v. Hobbs, 89 Eng. Rep. 836 (1680)). The Gomez court relied on a line of cases originating with Lovett in order to hold that Disneyland was a common carrier.
Second, a small number of important British statutes in effect at the time of the Revolution have been independently reenacted by U.S. states. Two examples are the Statute of Frauds (still widely known in the U.S. by that name) and the Statute of 13 Elizabeth (the ancestor of the Uniform Fraudulent Transfer Act). Such English statutes are still regularly cited in contemporary American cases interpreting their modern American descendants.See, e.g., Phillippe v. Shapell Industries, 43 Cal. 3d 1247, 241 Cal. Rptr. 22, 743 P.2d 1279 (1987) (citing original Statute of Frauds from England) and Meija v. Reed, 31 Cal.4th 657, 3 Cal. Rptr. 3d 390, 74 P.3d 166 (2003) (citing Statute of 13 Elizabeth).
Despite the presence of reception statutes, much of contemporary American common law has diverged significantly from English common law.Burnham, 43–44. Although the courts of the various Commonwealth nations are often influenced by each other's rulings, American courts rarely follow post-Revolution precedents from England or the British Commonwealth.
Early on, American courts, even after the Revolution, often did cite contemporary English cases, because appellate decisions from many American courts were not regularly reported until the mid-19th century. Lawyers and judges used English legal materials to fill the gap. Citations to English decisions gradually disappeared during the 19th century as American courts developed their own principles to resolve the legal problems of the American people.Elizabeth Gaspar Brown, "Frontier Justice: Wayne County 1796–1836", in Essays in Nineteenth-Century American Legal History, ed. Wythe Holt, 676–703 (Westport, CT: Greenwood Press, 1976): 686. Between 1808 and 1828, the briefs filed in court cases in the Territory of Michigan changed from a complete reliance on English sources of law to an increasing reliance on citations to American sources. The number of published volumes of American reports soared from eighteen in 1810 to over 8,000 by 1910. By 1879 one of the delegates to the California constitutional convention was already complaining: "Now, when we require them to state the reasons for a decision, we do not mean they shall write a hundred pages of detail. We [do] not mean that they shall include the small cases, and impose on the country all this fine judicial literature, for the Lord knows we have got enough of that already."People v. Kelly, 40 Cal.4th 106, 51 Cal. Rptr. 3d 98, 146 P.3d 547 (2006).
Today, in the words of Stanford law professor Lawrence M. Friedman: "American cases rarely cite foreign materials. Courts occasionally cite a British classic or two, a famous old case, or a nod to Blackstone; but current British law almost never gets any mention." Foreign law has never been cited as binding precedent, but as a reflection of the shared values of Anglo-American civilization or even Western civilization in general.See Lawrence v. Texas, 538 U.S. 558 (2003), in which the majority cited a European court decision, Dudgeon v. United Kingdom, 45 Eur. Ct. H. R. (1981), as indicative of the shared values of Western civilization.
Levels of law
Federal law
Federal law originates with the Constitution, which gives Congress the power to introduce legislation that the president may sign into law for certain limited purposes like regulating interstate commerce. The United States Code is the official compilation and codification of the general and permanent federal statutes. Many statutes give executive branch agencies the power to create regulations, which are published in the Federal Register and codified into the Code of Federal Regulations. From 1984 to 2024, regulations generally also carried the force of law under the Chevron doctrine, but are now subject only to a lesser form of judicial deference known as Skidmore deference. Many lawsuits turn on the meaning of a federal statute or regulation, and judicial interpretations of such meaning carry legal force under the principle of stare decisis.
During the 18th and 19th centuries, federal law traditionally focused on areas where there was an express grant of power to the federal government in the federal Constitution, like the military, money, foreign relations (especially international treaties), tariffs, intellectual property (specifically patents and copyrights), and mail. Since the start of the 20th century, broad interpretations of the Commerce and Spending Clauses of the Constitution have enabled federal law to expand into areas like aviation, telecommunications, railroads, pharmaceuticals, antitrust, and trademarks. In some areas, like aviation and railroads, the federal government has developed a comprehensive scheme that preempts virtually all state law, while in others, like family law, a relatively small number of federal statutes (generally covering interstate and international situations) interacts with a much larger body of state law. In areas like antitrust, trademark, and employment law, there are powerful laws at both the federal and state levels that coexist with each other. In a handful of areas like insurance, Congress has enacted laws expressly refusing to regulate them as long as the states have laws regulating them (see, e.g., the McCarran–Ferguson Act).
Statutes
After the president signs a bill into law (or Congress enacts it over the president's veto), it is delivered to the Office of the Federal Register (OFR) of the National Archives and Records Administration (NARA) where it is assigned a law number, and prepared for publication as a slip law. Public laws, but not private laws, are also given legal statutory citation by the OFR. At the end of each session of Congress, the slip laws are compiled into bound volumes called the United States Statutes at Large, and they are known as session laws. The Statutes at Large present a chronological arrangement of the laws in the exact order that they have been enacted.