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1.3: Sources and Types of Law

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    The American legal system is made up of many types of codified forms of law, with the United States Constitution being the pre-eminent source of American law. The Constitution establishes the boundaries of federal law, and it must be followed by all citizens, organizations, and entities. It includes Congressional acts, Senate-ratified treaties, executive regulations, and federal case law. The United States Code (“USC”) compiles these laws.

    American law mainly originates from constitutional law, statutory law, treaties, administrative regulations, and common law (which includes case law).

    The Constitution

    The United States Constitution is the foremost law of the land. The Constitution’s first ten amendments are referred to as the Bill of Rights, which offers specific protections of individual liberty and justice. Additionally, the Bill of Rights restricts certain powers of government. The Constitution empowers federal law making by giving Congress the power to enact statutes for certain limited purposes, like regulating interstate commerce. The United States Code officially compiles and codifies the federal statutes.

    fig 1.2.1.jpg
    Figure \(\PageIndex{1}\): The U.S. Constitution is known as the supreme law of the land. (Credit: lynn0101/ pixabay/ License: CC0)

    American Common Law

    As discussed in the previous section, the United States follows the common law legal tradition of English law. Judges in the Common Law system help shape the law through their rulings and interpretations. This body of past decisions is known as case law, which is used by judges to inform their own rulings. In fact, judges rely on precedent, i.e., previous court rulings on similar cases, when determining the ruling in their own cases.

    An example of how case law works is the case of the State v. Wayfair Inc. (2017 SD 56, 901 N.W.2d 754 (S.D. 2017), cert. granted, 138 S. Ct. 735 (2018)), in which the South Dakota Supreme Court held that a state law requiring internet retailers without an in-state physical presence to remit sales tax was unconstitutional. Unless this ruling is overruled by the United States Supreme Court, then it becomes part of the case law and precedent set in that state, and it will be followed by subsequent rulings when similar cases are filed.

    Federal Law

    The Constitution empowers federal law making by giving Congress the power to enact statutes for certain limited purposes, like regulating interstate commerce. Federal law preempts conflicting state and local laws. However, federal preemption is not without limits, insofar as states each have their own constitution and are considered sovereign. Therefore, federal law may only preempt state law if it is enacted within the limited powers that are enumerated and granted to Congress in the Constitution.

    Broad interpretations of the Constitution’s Commerce and Spending Clauses have expanded the reach of federal law into many areas. Indeed, its reach in some areas, such as aviation and railroads, is now so broad that it preempts virtually all state law. In others areas, such as family law, lawmaking continues to be left to the states. Finally, a number of powerful federal and state laws coexist in areas such as antitrust, trademark, employment law, and others.


    When a bill becomes a federal law, it is assigned a law number and prepared for publication by the Office of the Federal Register (OFR) of the National Archives and Records Administration (NARA). Public laws are also given legal statutory citation by the OFR and are incorporated into the United States Code (USC).


    Laws differ from regulations in that laws are passed by either the U.S. Congress or state congresses. Regulations, by contrast, are standards and rules adopted by administrative agencies that govern how laws will be enforced.

    Federal agencies often enjoy broad rulemaking authority when Congress acts to grant them this power. Called “regulations,” these agency rules normally carry the force of law, as long as they demonstrate a reasonable interpretation of the relevant statutes. For example, the Environmental Protection Agency (EPA) has established regulations for businesses and their emission and disposal of pollutants to protect the environment. The EPA has the authority to enforce these regulations when a business violates them, and such enforcement is usually done by fining the company or by using other means.

    The Administrative Procedure Act (APA) enables the adoption of regulations, which are codified and incorporated into the Code of Federal Regulations (CFR). Federal agencies frequently draft and distribute forms, manuals, policy statements, letters, and rulings. Though these may be considered as persuasive authority by the courts, they do not carry the same force as law. In other words, if a person or business questions a regulation of a government agency, saying it is unconstitutional, and that party is successful in proving it, then the regulation is not enforced and the agency will need to revise it or remove it.

    State Law

    America, as diverse as its fifty states, is also governed by fifty different state constitutions, state governments, and state courts. Each has its own legislative, executive, and judicial branches. States are empowered to create legislation that is related to matters not preempted by the federal Constitution and federal laws. Most cases involve state law issues and are litigated in state courts.

    Local Law

    In addition to federal and state law, municipalities, towns or cities, and counties may enact their own laws that do not conflict with state or federal laws.

    As demonstrated, American law does not draw from one source alone; instead, it is derived from many sources.

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