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1.4 Sources of Law and Their Priority

Learning Objectives

  1. Describe the different sources of law in the US legal system and the principal institutions that create those laws.
  2. Explain in what way a statute is like a treaty, and vice versa.
  3. Explain why the Constitution is “prior” and has priority over the legislative acts of a majority, whether in the US Congress or in a state legislature.
  4. Describe the origins of the common-law system and what common law means.

Sources of Law

In the United States today, there are numerous sources of law. The main ones are (1) constitutions—both state and federal, (2) statutes and agency regulations, and (3) judicial decisions. In addition, chief executives (the president and the various governors) can issue executive orders that have the effect of law.

In international legal systems, sources of law include treatiesFormal agreements concluded between nation-states. (agreements between states or countries) and what is known as customary international law (usually consisting of judicial decisions from national court systems where parties from two or more nations are in a dispute).

As you might expect, these laws sometimes conflict: a state law may conflict with a federal law, or a federal law might be contrary to an international obligation. One nation’s law may provide one substantive rule, while another nation’s law may provide a different, somewhat contrary rule to apply. Not all laws, in other words, are created equal. To understand which laws have priority, it is essential to understand the relationships between the various kinds of law.


ConstitutionsThe founding documents of any nation-state’s legal system. are the foundation for a state or nation’s other laws, providing the country’s legislative, executive, and judicial framework. Among the nations of the world, the United States has the oldest constitution still in use. It is difficult to amend, which is why there have only been seventeen amendments following the first ten in 1789; two-thirds of the House and Senate must pass amendments, and three-fourths of the states must approve them.

The nation’s states also have constitutions. Along with providing for legislative, executive, and judicial functions, state constitutions prescribe various rights of citizens. These rights may be different from, and in addition to, rights granted by the US Constitution. Like statutes and judicial decisions, a constitution’s specific provisions can provide people with a “cause of action” on which to base a lawsuit (see Section 1.4.3 "Causes of Action, Precedent, and " on “causes of action”). For example, California’s constitution provides that the citizens of that state have a right of privacy. This has been used to assert claims against businesses that invade an employee’s right of privacy. In the case of Virginia Rulon-Miller, her employer, International Business Machines (IBM), told her to stop dating a former colleague who went to work for a competitor. When she refused, IBM terminated her, and a jury fined the company for $300,000 in damages. As the California court noted, “While an employee sacrifices some privacy rights when he enters the workplace, the employee’s privacy expectations must be balanced against the employer’s interests.…[T]he point here is that privacy, like the other unalienable rights listed first in our Constitution…is unquestionably a fundamental interest of our society.”Rulon-Miller v. International Business Machines Corp., 162 Cal. App.3d 241, 255 (1984).

Statutes and Treaties in Congress

In Washington, DC, the federal legislature is known as Congress and has both a House of Representatives and a Senate. The House is composed of representatives elected every two years from various districts in each state. These districts are established by Congress according to population as determined every ten years by the census, a process required by the Constitution. Each state has at least one district; the most populous state (California) has fifty-two districts. In the Senate, there are two senators from each state, regardless of the state’s population. Thus Delaware has two senators and California has two senators, even though California has far more people. Effectively, less than 20 percent of the nation’s population can send fifty senators to Washington.

Many consider this to be antidemocratic. The House of Representatives, on the other hand, is directly proportioned by population, though no state can have less than one representative.

Each Congressional legislative body has committees for various purposes. In these committees, proposed bills are discussed, hearings are sometimes held, and bills are either reported out (brought to the floor for a vote) or killed in committee. If a bill is reported out, it may be passed by majority vote. Because of the procedural differences between the House and the Senate, bills that have the same language when proposed in both houses are apt to be different after approval by each body. A conference committee will then be held to try to match the two versions. If the two versions differ widely enough, reconciliation of the two differing versions into one acceptable to both chambers (House and Senate) is more difficult.

If the House and Senate can agree on identical language, the reconciled bill will be sent to the president for signature or veto. The Constitution prescribes that the president will have veto power over any legislation. But the two bodies can override a presidential veto with a two-thirds vote in each chamber.

In the case of treaties, the Constitution specifies that only the Senate must ratify them. When the Senate ratifies a treaty, it becomes part of federal law, with the same weight and effect as a statute passed by the entire Congress. The statutes of Congress are collected in codified form in the US Code. The code is available online at

Delegating Legislative Powers: Rules by Administrative Agencies

Congress has found it necessary and useful to create government agencies to administer various laws (see Chapter 5 "Administrative Law"). The Constitution does not expressly provide for administrative agencies, but the US Supreme Court has upheld the delegation of power to create federal agencies.

Examples of administrative agencies would include the Occupational Safety and Health Administration (OSHA), the Environmental Protection Agency (EPA), and the Federal Trade Commission (FTC).

It is important to note that Congress does not have unlimited authority to delegate its lawmaking powers to an agency. It must delegate its authority with some guidelines for the agency and cannot altogether avoid its constitutional responsibilities (see Chapter 5 "Administrative Law").

Agencies propose rules in the Federal Register, published each working day of the year. Rules that are formally adopted are published in the Code of Federal Regulations, or CFR, available online at

State Statutes and Agencies: Other Codified Law

Statutes are passed by legislatures and provide general rules for society. States have legislatures (sometimes called assemblies), which are usually made up of both a senate and a house of representatives. Like the federal government, state legislatures will agree on the provisions of a bill, which is then sent to the governor (acting like the president for that state) for signature. Like the president, governors often have a veto power. The process of creating and amending, or changing, laws is filled with political negotiation and compromise.

On a more local level, counties and municipal corporations or townships may be authorized under a state’s constitution to create or adopt ordinances. Examples of ordinances include local building codes, zoning laws, and misdemeanors or infractions such as skateboarding or jaywalking. Most of the more unusual laws that are in the news from time to time are local ordinances. For example, in Logan County, Colorado, it is illegal to kiss a sleeping woman; in Indianapolis, Indiana, and Eureka, Nebraska, it is a crime to kiss if you have a mustache. But reportedly, some states still have odd laws here and there. Kentucky law proclaims that every person in the state must take a bath at least once a year, and failure to do so is illegal.

Judicial Decisions: The Common Law

Common lawJudicial decisions that do not involve interpretation of statutes, regulations, treaties, or the Constitution. consists of decisions by courts (judicial decisions) that do not involve interpretation of statutes, regulations, treaties, or the Constitution. Courts make such interpretations, but many cases are decided where there is no statutory or other codified law or regulation to be interpreted. For example, a state court deciding what kinds of witnesses are required for a valid will in the absence of a rule (from a statute) is making common law.

United States law comes primarily from the tradition of English common law. By the time England’s American colonies revolted in 1776, English common-law traditions were well established in the colonial courts. English common law was a system that gave written judicial decisions the force of law throughout the country. Thus if an English court delivered an opinion as to what constituted the common-law crime of burglary, other courts would stick to that decision, so that a common body of law developed throughout the country. Common law is essentially shorthand for the notion that a common body of law, based on past written decisions, is desirable and necessary.

In England and in the laws of the original thirteen states, common-law decisions defined crimes such as arson, burglary, homicide, and robbery. As time went on, US state legislatures either adopted or modified common-law definitions of most crimes by putting them in the form of codes or statutes. This legislative ability—to modify or change common law into judicial law—points to an important phenomenon: the priority of statutory law over common law. As we will see in the next section, constitutional law will have priority over statutory law.

Priority of Laws

The Constitution as Preemptive Force in US Law

The US Constitution takes precedence over all statutes and judicial decisions that are inconsistent. For example, if Michigan were to decide legislatively that students cannot speak ill of professors in state-sponsored universities, that law would be void, since it is inconsistent with the state’s obligation under the First Amendment to protect free speech. Or if the Michigan courts were to allow a professor to bring a lawsuit against a student who had said something about him that was derogatory but not defamatory, the state’s judicial system would not be acting according to the First Amendment. (As we will see in Chapter 7 "Introduction to Tort Law", free speech has its limits; defamation was a cause of action at the time the First Amendment was added to the Constitution, and it has been understood that the free speech rights in the First Amendment did not negate existing common law.)

Statutes and Cases

Statutes generally have priority, or take precedence, over case law (judicial decisions). Under common-law judicial decisions, employers could hire young children for difficult work, offer any wage they wanted, and not pay overtime work at a higher rate. But various statutes changed that. For example, the federal Fair Labor Standards Act (1938) forbid the use of oppressive child labor and established a minimum pay wage and overtime pay rules.

Treaties as Statutes: The “Last in Time” Rule

A treaty or convention is considered of equal standing to a statute. Thus when Congress ratified the North American Free Trade Agreement (NAFTA), any judicial decisions or previous statutes that were inconsistent—such as quotas or limitations on imports from Mexico that were opposite to NAFTA commitments—would no longer be valid. Similarly, US treaty obligations under the General Agreement on Tariffs and Trade (GATT) and obligations made later through the World Trade Organization (WTO) would override previous federal or state statutes.

One example of treaty obligations overriding, or taking priority over, federal statutes was the tuna-dolphin dispute between the United States and Mexico. The Marine Mammal Protection Act amendments in 1988 spelled out certain protections for dolphins in the Eastern Tropical Pacific, and the United States began refusing to allow the importation of tuna that were caught using “dolphin-unfriendly” methods (such as purse seining). This was challenged at a GATT dispute panel in Switzerland, and the United States lost. The discussion continued at the WTO under its dispute resolution process. In short, US environmental statutes can be ruled contrary to US treaty obligations.

Under most treaties, the United States can withdraw, or take back, any voluntary limitation on its sovereignty; participation in treaties is entirely elective. That is, the United States may “unbind” itself whenever it chooses. But for practical purposes, some limitations on sovereignty may be good for the nation. The argument goes something like this: if free trade in general helps the United States, then it makes some sense to be part of a system that promotes free trade; and despite some temporary setbacks, the WTO decision process will (it is hoped) provide far more benefits than losses in the long run. This argument invokes utilitarian theory (that the best policy does the greatest good overall for society) and David Ricardo’s theory of comparative advantage.

Ultimately, whether the United States remains a supporter of free trade and continues to participate as a leader in the WTO will depend upon citizens electing leaders who support the process. Had Ross Perot been elected in 1992, for example, NAFTA would have been politically (and legally) dead during his term of office.

Causes of Action, Precedent, and Stare Decisis

No matter how wrong someone’s actions may seem to you, the only wrongs you can right in a court are those that can be tied to one or more causes of actionIn a complaint, a legal basis on which a claim is predicated. The legal basis can be a Constitutional law, a statute, a regulation, or a prior judicial decision that creates a precedent to be followed.. Positive law is full of cases, treaties, statutes, regulations, and constitutional provisions that can be made into a cause of action. If you have an agreement with Harold Hill that he will purchase seventy-six trombones from you and he fails to pay for them after you deliver, you will probably feel wronged, but a court will only act favorably on your complaint if you can show that his behavior gives you a cause of action based on some part of your state’s contract law. This case would give you a cause of action under the law of most states; unless Harold Hill had some legal excuse recognized by the applicable state’s contract law—such as his legal incompetence, his being less than eighteen years of age, his being drunk at the time the agreement was made, or his claim that the instruments were trumpets rather than trombones or that they were delivered too late to be of use to him—you could expect to recover some compensation for his breaching of your agreement with him.

An old saying in the law is that the law does not deal in trifles, or unimportant issues (in Latin, de minimis non curat lex). Not every wrong you may suffer in life will be a cause to bring a court action. If you are stood up for a Saturday night date and feel embarrassed or humiliated, you cannot recover anything in a court of law in the United States, as there is no cause of action (no basis in the positive law) that you can use in your complaint. If you are engaged to be married and your spouse-to-be bolts from the wedding ceremony, there are some states that do provide a legal basis on which to bring a lawsuit. “Breach of promise to marry” is recognized in several states, but most states have abolished this cause of action, either by judicial decision or by legislation. Whether a runaway bride or groom gives rise to a valid cause of action in the courts depends on whether the state courts still recognize and enforce this now-disappearing cause of action.

Your cause of action is thus based on existing laws, including decided cases. How closely your case “fits” with a prior decided case raises the question of precedent.

As noted earlier in this chapter, the English common-law tradition placed great emphasis on precedent and what is called stare decisis. A court considering one case would feel obliged to decide that case in a way similar to previously decided cases. Written decisions of the most important cases had been spread throughout England (the common “realm”), and judges hoped to establish a somewhat predictable, consistent group of decisions.

The English legislature (Parliament) was not in the practice of establishing detailed statutes on crimes, torts, contracts, or property. Thus definitions and rules were left primarily to the courts. By their nature, courts could only decide one case at a time, but in doing so they would articulate holdings, or general rules, that would apply to later cases.

Suppose that one court had to decide whether an employer could fire an employee for no reason at all. Suppose that there were no statutes that applied to the facts: there was no contract between the employer and the employee, but the employee had worked for the employer for many years, and now a younger person was replacing him. The court, with no past guidelines, would have to decide whether the employee had stated a “cause of action” against the employer. If the court decided that the case was not legally actionable, it would dismiss the action. Future courts would then treat similar cases in a similar way. In the process, the court might make a holding that employers could fire employees for any reason or for no reason. This rule could be applied in the future should similar cases come up.

But suppose that an employer fired an employee for not committing perjury (lying on the witness stand in a court proceeding); the employer wanted the employee to cover up the company's criminal or unethical act. Suppose that, as in earlier cases, there were no applicable statutes and no contract of employment. Courts relying on a holding or precedent that “employers may fire employees for any reason or no reason” might rule against an employee seeking compensation for being fired for telling the truth on the witness stand. Or it might make an exception to the general rule, such as, “Employers may generally discharge employees for any reason or for no reason without incurring legal liability; however, employers will incur legal liability for firing an employee who refuses to lie on behalf of the employer in a court proceeding.”

In each case (the general rule and its exception), the common-law tradition calls for the court to explain the reasons for its ruling. In the case of the general rule, “freedom of choice” might be the major reason. In the case of the perjury exception, the efficiency of the judicial system and the requirements of citizenship might be used as reasons. Because the court’s “reasons” will be persuasive to some and not to others, there is inevitably a degree of subjectivity to judicial opinions. That is, reasonable people will disagree as to the persuasiveness of the reasoning a court may offer for its decision.

Written judicial opinions are thus a good playing field for developing critical thinking skills by identifying the issue in a case and examining the reasons for the court’s previous decision(s), or holding. What has the court actually decided, and why? Remember that a court, especially the US Supreme Court, is not only deciding one particular case but also setting down guidelines (in its holdings) for federal and state courts that encounter similar issues. Note that court cases often raise a variety of issues or questions to be resolved, and judges (and attorneys) will differ as to what the real issue in a case is. A holding is the court’s complete answer to an issue that is critical to deciding the case and thus gives guidance to the meaning of the case as a precedent for future cases.

Beyond the decision of the court, it is in looking at the court’s reasoning that you are most likely to understand what facts have been most significant to the court and what theories (schools of legal thought) each trial or appellate judge believes in. Because judges do not always agree on first principles (i.e., they subscribe to different schools of legal thought), there are many divided opinions in appellate opinions and in each US Supreme Court term.

Key Takeaway

There are different sources of law in the US legal system. The US Constitution is foundational; US statutory and common law cannot be inconsistent with its provisions. Congress creates statutory law (with the signature of the president), and courts will interpret constitutional law and statutory law. Where there is neither constitutional law nor statutory law, the courts function in the realm of common law. The same is true of law within the fifty states, each of which also has a constitution, or foundational law.

Both the federal government and the states have created administrative agencies. An agency only has the power that the legislature gives it. Within the scope of that power, an agency will often create regulations (see Chapter 5 "Administrative Law"), which have the same force and effect as statutes. Treaties are never negotiated and concluded by states, as the federal government has exclusive authority over relations with other nation-states. A treaty, once ratified by the Senate, has the same force and effect as a statute passed by Congress and signed into law by the president.

Constitutions, statutes, regulations, treaties, and court decisions can provide a legal basis in the positive law. You may believe you have been wronged, but for you to have a right that is enforceable in court, you must have something in the positive law that you can point to that will support a cause of action against your chosen defendant.


  1. Give one example of where common law was overridden by the passage of a federal statute.
  2. How does common law change or evolve without any action on the part of a legislature?
  3. Lindsey Paradise is not selected for her sorority of choice at the University of Kansas. She has spent all her time rushing that particular sorority, which chooses some of her friends but not her. She is disappointed and angry and wants to sue the sorority. What are her prospects of recovery in the legal system? Explain.