When a lawyer is asked a question, the first job is to find the law that answers it. American law does not live in one book. It comes from several sources, made by different bodies, and they rank in an order of authority. This lesson builds on what law is.
| Source | Made by | Example |
|---|---|---|
| Constitutions | the people, through ratification (federal and each state) | the First Amendment; a state constitution's right to a public education |
| Statutes | Congress and state legislatures | the Clean Air Act; a state's criminal code |
| Treaties | the President, with two-thirds of the Senate | a tax treaty with Canada |
| Regulations (administrative law) | agencies, under power a statute delegates | a federal rule on food labels in the Code of Federal Regulations |
| Case law | courts, deciding cases | the common law of contracts; a court's reading of a statute |
| Ordinances | cities and counties | a zoning rule; a leash law |
| Executive orders | the President or a governor, directing officials | an order on how agencies manage hiring |
Key idea
American law comes from constitutions, statutes, treaties, regulations, court decisions and ordinances. They rank in an order: the U.S. Constitution is highest, then valid federal statutes and treaties, then federal regulations; within a state, its constitution outranks its statutes, which outrank its regulations and local ordinances.
Why it works
Why an order? Because each lower source gets its authority from a higher one. An agency may write a regulation only because a statute gave it that power, so a regulation that goes beyond the statute is invalid. A legislature may pass statutes only within the limits of its constitution, so an unconstitutional statute is void. Follow the chain upward and you reach the people, who adopted the constitutions. Courts sit beside this ladder: they decide cases under every source and, where no statute speaks, they apply the common law they have built case by case.
Worked example: A regulation that goes too far
A statute lets an agency set safety rules for "commercial trucks." The agency issues a rule for private pickup trucks used only for family errands. Is the rule valid?
- Find the source of the agency's power: the statute.
- The statute reaches commercial trucks. Family pickups are not commercial.
- A regulation cannot go beyond the authority the statute delegates.
Answer: No. The rule exceeds the statute, so a court would set it aside.
Worked example: A city against its state
A state statute sets the speed limit on all state highways at 65 mph. A town passes an ordinance setting 55 mph on the state highway that runs through it, and the statute does not allow towns to change it. Which rule controls?
- Ordinances rank below state statutes. Cities and counties have only the powers their state gives them.
- The two rules conflict on the same road.
- Unless state law lets the town set its own limit, the state statute controls.
Answer: The state statute (65 mph).
Lawyers also separate primary authority (the law itself: the sources above) from secondary authority (writing about the law: treatises, law review articles, the Restatements). Secondary sources can explain and persuade, but they are not law.
Common mistake
Thinking only legislatures make law. Agencies write binding regulations (the Federal Register, where they are published, runs to tens of thousands of pages a year), courts make the common law and interpret every other source, and the people make constitutions. A quick check: ask "who made this rule, and where did they get the power to make it?"
This is an educational course, not legal advice.