The United States runs two court systems at once — federal and state — under one Constitution, and most people never need to understand how they fit together until a specific problem lands in one of them. This covers the basic structure: how power is divided between federal and state government, the difference between criminal and civil law, where the rules actually come from, and how a court case moves from a trial court to the U.S. Supreme Court.
Two Governments, One Country
The Constitution set up federalism: a national government and 50 state governments, each with real authority, operating in the same territory at the same time. Neither is a branch office of the other.
The Tenth Amendment states the default rule: “The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.” The federal government only has the powers the Constitution actually gives it — among them, coining money, regulating interstate and foreign commerce, declaring war, and making the laws needed to carry out those powers. Everything else defaults to the states.
Where the two do overlap and conflict, the Constitution’s Supremacy Clause makes federal law control. In practice this rarely comes up as a head-on collision; state and federal law more often run in parallel — concurrent jurisdiction — than fight over the same ground.
Criminal Law vs. Civil Law
Nearly everything in American law sorts into one of two broad categories.
- Criminal law is the state prosecuting someone for an offense against the public order — theft, assault, fraud. The state brings the case, and the standard of proof is “beyond a reasonable doubt,” the highest standard in American law.
- Civil law covers everything else, including contract disputes and torts — a wrong done to a specific person, such as a car accident or a breach of a written agreement. A private person or company brings the case, and the standard of proof is much lower: a “preponderance of the evidence,” meaning more likely than not.
The same underlying event can trigger both. A person who assaults someone can be criminally prosecuted by the state and separately sued for damages by the victim — two different cases, two different standards of proof, and it is entirely possible to be acquitted in one and held liable in the other. Most cases, criminal or civil, never reach a jury; the large majority are resolved by a plea or a settlement before trial.
Where the Rules Come From
Modern American law comes from three sources, and most real cases involve more than one of them.
- Constitutions — federal and state — set the outer limits on what any law can require, and create the legislatures that write the rest.
- Statutes, passed by Congress at the federal level and by state legislatures at the state level (city councils pass the local version, called ordinances). This is where the great majority of today’s law lives, including the definitions of specific crimes and their penalties in each state’s penal code.
- Case law, also called common law — the body of written appellate court decisions that interpret and fill gaps in the statutes. Once an appellate court decides an issue, that decision becomes a precedent that guides how similar cases are decided later, a principle called stare decisis — Latin for “to stand by things decided.”
A crime committed in one state may not be a crime in another; local ordinances only apply inside their own city or county. When conduct violates both a state law and a federal law — drug offenses are a common example — more than one jurisdiction can have the authority to prosecute the same act.
Trial Courts and Appellate Courts
Every state system and the federal system both split into two functionally different kinds of court.
- Trial courts are where a case actually begins — witnesses testify, evidence is presented, and a judge or jury decides the facts. In the federal system these are the U.S. District Courts, one or more per state, organized into 94 judicial districts nationwide. States use various names — district, superior, circuit, or county court — for the equivalent.
- Appellate courts don’t hold trials or hear new evidence. They review the trial record for legal error and either affirm the decision, reverse it, or send it back (remand) for further proceedings. There are 13 U.S. Courts of Appeals — one for each of 11 numbered circuits, one for the D.C. Circuit, and one for the Federal Circuit.
- The U.S. Supreme Court sits above all of them, hearing appeals from the circuit courts and federal questions coming up from state supreme courts. It has almost complete discretion over which cases it hears, and it takes only a small fraction of the cases appealed to it each year — for most litigants, the court of appeals is effectively the last stop.
Most state trial courts have “general jurisdiction,” meaning they can hear a broad mix of criminal and civil cases. Some states also run specialized trial courts — family court, small claims, drug court — for particular kinds of cases.
See also where our legal system came from and how a civil lawsuit works.