Sources of Law
In the United States, our laws come primarily from:
Federal and state constitutions;
Statutory law from Congress, the state legislatures, and local legislative bodies;
Common law from federal and state appellate courts;
Administrative law (rules and regulations) from government agencies;
Treaties and conventions; and
Executive orders.
🎞️ Watch and Learn: Sources of Law
Constitutions
Federal/National
The most fundamental law in the United States is the U.S. Constitution, which is the supreme law of the nation. Any law that conflicts with it is void. The Constitution serves three important functions. First, it establishes the structure of our national government and identifies the powers of the legislative, executive, and judicial branches. Second, it defines the boundaries of each branch’s authority and creates “checks” on each branch by the other branches. For example, the president is the commander-in-chief of the armed forces but does not have the power to declare war. That duty falls to Congress. And third, the Constitution guarantees civil liberties and individual rights.
The power granted to the federal government by the Constitution is limited. Any powers not expressly granted to the federal government by the Constitution are reserved to the states. This means that if the Constitution does not give the federal government power over a particular area, then the states regulate it.
The first ten amendments to the Constitution are known as the Bill of Rights. Despite the limited power granted to the federal government by the Constitution, the Bill of Rights protects certain individual civil rights and liberties from governmental interference. These rights include the freedom of speech and religion, the right to bear arms, and the rights of individuals who are suspected and accused of crimes.
Figure Separation of Powers of the Federal Government
State
In the United States, each state also has its own constitution, which serves essentially the same function for the state government as the U.S. Constitution serves for the federal government. Specifically, state constitutions establish limits of state government power, establish the organization and duties of the different branches of government at the state level, and protect fundamental rights of state citizens.
This dual system of government in the United States is called federalism, which is a governance structure whereby the federal government and the state governments coexist through a shared power scheme.
Figure Separation of powers of state governments
🔍 Constitutional Law: Example of Government and Private Acts
Cora stands on a public sidewalk and criticizes the President's foreign relations policies. Although other individuals may be annoyed by Cora’s words, the government cannot arrest or criminally prosecute Cora for her speech because the First Amendment of the U.S. Constitution guarantees each individual the right to speak freely.
On the other hand, if Cora walks into a retail department store and criticizes the owner, the owner could eject Cora immediately. The store and its personnel are private, not the government, and they do not need to provide the same freedoms the Constitution provides.
Exceptions to Constitutional Protections
The federal and state constitutions are both written with words that can be subject to more than one interpretation. Thus, there are many exceptions to any constitution’s protections.
For safety and security reasons, we see more exceptions to constitutional protections in public schools and prisons. For example, public schools and prisons can mandate a certain style of dress for the purpose of ensuring safety. Technically, forcing an individual to dress a specific way could violate the right to self-expression, which the First Amendment guarantees. However, if wearing a uniform can lower gang-related conflicts in school and prevent prisoners from successfully escaping, the government can constitutionally suppress free speech in these locations.
For safety and security reasons, we see more limitations and exceptions to constitutional protections in public schools and prisons. For example, public schools and prisons can mandate a certain style of dress for the purpose of ensuring safety. Technically, forcing an individual to dress a specific way could violate the right to self-expression, which the First Amendment guarantees. However, if wearing a uniform can lower gang-related conflicts in school and prevent prisoners from successfully escaping, the government can constitutionally suppress free speech in these locations.
Supremacy of the U.S. Constitution
Of all sources of law in the United States, the U.S. Constitution is considered the highest and should not be supplanted by either of the other two sources of law. Pursuant to principles of federal supremacy, the U.S. Constitution is the most preeminent source of law, and state constitutions cannot supersede it.
Statutes
While the Constitution applies to government action, statutes apply to and regulate individual or private action. A statute is a written (and published) law that can be enacted in one of two ways. Most statutes are written and voted into law by the legislative branch of government. This is simply a group of individuals elected for this purpose. The U.S. legislative branch is called Congress, and Congress votes federal statutes into law. Every state has a legislative branch as well, called a state legislature, and a state legislature votes state statutes into law. Often, states codify their criminal statutes into a penal code.
🔍 The Model Penal Code
Despite its name, the Model Penal Code is not enforceable statutory law. Criminal laws differ significantly from state to state, so in the early 1960s, a group of legal scholars, lawyers, and judges who were members of the American Law Institute drafted a set of suggested criminal statutes called the Model Penal Code.
The intent of the Model Penal Code was to provide a standardized set of criminal statutes that all states could adopt, thus simplifying the diversity effect of the United States legal system. While the Model Penal Code has not been universally adopted, a majority of the states have incorporated portions of it into their penal codes, and the Model Penal Code survives as a guideline and focal point for discussion when state legislatures modify their criminal statutes.
Ordinances
Ordinances are similar to statutes, except that cities and counties vote them into law, rather than a state’s legislature or a state’s citizens. Ordinances usually relate to health, safety, or welfare, and violations of them are typically classified as infractions or misdemeanors, rather than felonies. A written law prohibiting jaywalking within a city’s or county’s limits is an example of an ordinance.
Administrative Rules and Regulations
Other written and published laws that apply to individuals are administrative laws (officially known as administrative rules but commonly referred to as regulations) and ordinances. Administrative laws and ordinances should not supersede or conflict with statutory law.
Administrative laws are enacted by administrative agencies, which are governmental agencies designed to regulate specific areas. Administrative agencies can be federal or state and contain not only a legislative branch but also an executive (enforcement) branch and a judicial (court) branch. The Food and Drug Administration (FDA) is an example of a federal administrative agency. The FDA regulates any food products or drugs produced and marketed in the United States.
Executive Orders
Executive orders are another type of administrative law. Article II, Section 1 of the U.S. Constitution gives the president the power to “take care that the laws be faithfully executed.” Under this power, the president may issue executive orders requiring officials in the executive branch to perform their duties in a particular manner. State governors have the same authority under state constitutions. Although they are not laws that apply directly to individuals and businesses, executive orders are important legal documents because they direct the government’s enforcement efforts.
More on Common Law (aka Case Law) and Stare Decisis
Binding legal principles also come from the courts. When appellate courts decide a case, they may interpret and apply legal principles in a way that are binding on lower courts in the future. The process of applying a prior appellate decision to a case is called precedent. Simply put, precedent is when judges use past decisions to guide them. The benefit of precedent is that it makes the law predictable and furthers the rule of law by applying legal principles to the greater community, not just individuals.
Rules of Stare Decisis and Use of Precedent
Case precedent is generally an appeal rather than a trial. There is often more than one level of appeal, so some appeals come from higher courts than others. Many complex rules govern the use of precedent. Lawyers primarily use precedent in their arguments, rather than statutes or the Constitution, because it is so specific. With proper research, lawyers can usually find precedent that matches or comes very close to matching the facts of any particular case. In the most general sense, judges tend to follow precedent that is newer, from a high court, and from the same court system, either federal or state.
🔍 Example of Stare Decisis and Use of Precedent
Geoffrey is a defense attorney for Conrad, who is on trial for first-degree murder. The murder prosecution is taking place in New Mexico. Geoffrey finds case precedent from a New York Court of Appeals decision dated 1999, indicating that Conrad should have been prosecuted for voluntary manslaughter, not first-degree murder.
Brandon, the prosecuting attorney, finds case precedent from the New Mexico Supreme Court, dated 2008, indicating that a first-degree murder prosecution is appropriate. The trial court will probably follow the precedent submitted by Brandon because it is newer, from a higher court, and from the same court system as the trial.
Common Law in the Criminal Context
In modern society, a general rule is that judges cannot create crimes. To do so would violate notions of fairness. Making up a new crime and punishing the defendant for it does not provide consistency or predictability to our legal system. It also violates the principle of legality, a core concept of American criminal justice embodied in this phrase: “Nullum crimen sine lege, nulla poena sine crimen” (No crime without law, no punishment without crime).
Generally, statutes (products of legislatures) must define criminal conduct. If no statute exists to criminalize the defendant’s behavior, the defendant cannot be criminally prosecuted, even if the behavior is abhorrent. As the Model Penal Code (see below) states, “[n]o conduct constitutes an offense unless it is a crime or violation under this Code or another statute of this State” Model Penal Code § 1.05(1). Also, it should be noted that although traditional criminal statutes designate particular conduct (such as intentionally causing another's death) as criminal, statutes may also declare that violating administrative laws can result in criminal punishment. For example, via 18 U.S.C. § 1520(b), Congress declared that violations of certain provisions of the Securities and Exchange Act of 1934 may result in imprisonment.
The common law still plays an important role in criminal lawmaking, even though most crimes are now embodied in statutes. Classification of crimes as felonies and misdemeanors is a reflection of English common law. Legislatures often create statutes out of former common law crimes. Judges look to the common law when defining statutory terms, establishing criminal procedure, and creating defenses to crimes. The United States is considered a common law country. Every state except Louisiana, which is influenced by the Napoleonic French Civil Code (and possibly Spanish Civil Code) adopts the common law as the law of the state except where a statute provides otherwise.
🔍 Example of a Court’s Refusal to Create a Common Law Crime
In Keeler v. Superior Court, 470 P.2d 617 (1970), the defendant attacked his pregnant ex-wife, and her baby was thereafter stillborn. The California Supreme Court disallowed a murder charge against Keeler under California Penal Code § 187 because the statute criminalized only the malicious killing of a “human being.” The court reached its decision after examining the common-law definition of "human being" and determined that the definition did not include a fetus.
The court reasoned that it could not create a new crime without violating the Due Process Clause, Separation of Powers, and California Penal Code § 6, which prohibits the creation of common-law crimes. After the Keeler decision, the California Legislature changed Penal Code § 187 to include a fetus, except for specific acts of a physician or the expectant mother .
The Integral Role of Case Law
Generally, if there is a statute on an issue, the statute is superior to case law, just as the Constitution is superior to statutory law. However, judges interpret constitutional and statutory law, making case law a powerful source of law. A judge can interpret a constitution in a way that adds or creates exceptions to its protections. A judge can also interpret a statute in a way that makes it unconstitutional and unenforceable. This is called the power of judicial review. Marbury v. Madison, 5 U.S. (1 Cranch) 137 (1803).
🔍 Example of Judicial Review
An example of judicial review is set forth in Texas v. Johnson, 491 U.S. 397 (1989). In Johnson, the U.S. Supreme Court ruled that burning a flag is protected self-expression under the First Amendment to the U.S. Constitution. Thus, the Court reversed the defendant’s conviction under a Texas statute that criminalized the desecration of a venerated object.
Note how Johnson not only (1) treated a state's laws as valid as long as it does not deprive its citizens of fundamental rights guaranteed by U.S. Constitution—a function of the 14th Amendment— but also (2) construed the First Amendment as if the Constitution clearly included flag burning as protected speech of speech.
Treaties and Conventions
A treaty is a binding agreement between two nations. A convention is a binding agreement among a group of nations. In the U.S., a treaty or convention is generally negotiated by the executive branch. To be binding, the U.S. Constitution requires the Senate to ratify treaties by a two-thirds vote. Once ratified, a treaty becomes part of federal law with the same weight and effect as a statute passed by the entire Congress. Therefore, treaties and conventions have equal standing as statutes in U.S. law.
Table Hierarchy of Sources of Law
Priority
Source
Comment
1
Constitutions
Exist at both federal and state levels
2 (tie)
Statutes
Laws passed by the federal or state legislatures
2 (tie)
Treaties and Conventions
International agreements that have the same standing as statutes
4
Judicial Opinions
Court interpretation and application of constitutions, statutes, treaties, agency regulations, and executive orders
5
Agency Regulations
Rules and regulations adopted by administrative agencies at the federal, state, or local level
6
Executive Orders
Guidance from the president or governor to executive branch officials about how to perform their duty
Attributions and Licensing
Except where otherwise noted, this page's content is adapted from 1.6 Sources of Law in Introduction to Criminal Law by Tara Storm, used under CC BY-NC-SA 3.0 
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