The US legal system is a layered framework in which a written Constitution sits above all other law, three branches of federal government share power, and a federal court system runs parallel to fifty separate state court systems that handle most everyday cases. Its roots are in English common law, but ratification of the United States Constitution in 1788 replaced that inherited tradition with a unified structure built around a single governing document. Everything else — statutes, regulations, court rulings, state law — fits beneath it in a defined order.
Where the Law Comes From
Legal authority follows a strict hierarchy. The Constitution comes first. Article VI calls it “the supreme Law of the Land,” and any statute, regulation, or ruling that conflicts with it is invalid.1Congress.gov. Constitution of the United States – Article VI
Statutes come next. Congress passes federal statutes, which are organized by subject into the United States Code. Title 26 covers the Internal Revenue Code, Title 35 handles patents, Title 18 addresses federal crimes. Each state legislature passes its own statutes, compiled into that state’s code. A statute is a deliberate written rule, and it overrides any conflicting common law or regulation on the same subject.
Administrative law fills the space between a broad statute and its day-to-day enforcement. When Congress tells an agency to regulate workplace safety or clean air standards, the agency writes detailed rules explaining how the law works in practice. Those rules sit in the Code of Federal Regulations and carry the force of law within their subject areas.2National Archives. About the Code of Federal Regulations
Common law is the body of rules built up through court decisions. Under the doctrine of stare decisis, judges follow the reasoning of prior cases when the facts are similar, which keeps the law predictable for anyone signing a contract or buying a house.3Federal Judicial Center. Stare Decisis Courts do overturn earlier decisions, but typically only when the prior reasoning was clearly flawed or circumstances have fundamentally changed.
Three Branches of Government
The first three articles of the Constitution divide federal authority among three branches, each with a distinct role that checks the others.
Article I vests “all legislative Powers” in Congress, made up of the Senate and the House of Representatives.4Congress.gov. Constitution of the United States – Article I Congress writes federal statutes, controls the budget, defines federal crimes, and confirms or rejects presidential appointments.
Article II places executive power in the President.5Congress.gov. Constitution of the United States – Article II The President enforces federal law through executive departments and agencies, commands the military, negotiates treaties, and issues executive orders directing how the executive branch does its work. Agencies like the Environmental Protection Agency and the Department of Labor sit within this branch.
Article III establishes the judiciary, vesting its power in “one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish.”6Congress.gov. Constitution of the United States – Article III Federal judges serve during “good Behaviour,” which in practice means for life. That insulation from elections lets courts make unpopular rulings when the law requires it.
The Constitution does not expressly give courts the power to strike down laws. The Supreme Court claimed that authority in Marbury v. Madison in 1803, when Chief Justice John Marshall wrote that “it is emphatically the province and duty of the judicial department to say what the law is.”7Congress.gov. ArtIII.S1.3 Marbury v. Madison and Judicial Review If the Constitution is supreme and a statute conflicts with it, the court must apply the Constitution. Judicial review is why courts can block executive orders, invalidate acts of Congress, and overturn state laws that violate federal constitutional protections.
Rights That Protect You in the System
The original Constitution set up the structure of government. Most of the rights people associate with American law come from the amendments. The Bill of Rights, ratified in 1791, added the first ten.8National Archives. The Bill of Rights – What Does it Say Several of them shape how the system treats anyone who comes into contact with it:
- The Fourth Amendment bars unreasonable searches and seizures. Police generally need a warrant based on probable cause before searching your home or belongings.
- The Fifth Amendment protects against being tried twice for the same offense, guarantees the right against self-incrimination, and requires due process before the government can take your life, liberty, or property. Serious federal criminal charges also require a grand jury indictment.9Legal Information Institute. Fifth Amendment
- The Sixth Amendment guarantees anyone accused of a crime a speedy public trial, an impartial jury, notice of the charges, the right to confront witnesses, and the assistance of counsel. If you cannot afford a lawyer in a criminal case, one is appointed for you.10Legal Information Institute. Sixth Amendment
- The Eighth Amendment prohibits excessive bail, excessive fines, and cruel and unusual punishment.
The Fourteenth Amendment, ratified after the Civil War, extended due process against state governments. Its Due Process Clause forbids any state from depriving “any person of life, liberty, or property, without due process of law.”11Congress.gov. Due Process Generally The Supreme Court has used this clause to apply most Bill of Rights protections to state and local governments. Without it, a state could in theory restrict speech or deny jury trials without violating the federal Constitution.
Federal Courts and State Courts
The country runs two parallel legal systems: a federal one and fifty state-level ones. The Tenth Amendment draws the boundary, reserving to the states or the people any powers the Constitution does not grant the federal government.12Congress.gov. Constitution of the United States – Tenth Amendment In practice, most of the law that affects your daily life comes from your state. Family law, real estate transactions, personal injury cases, most criminal prosecutions, contract disputes, and traffic violations run through state systems. State courts handle the vast majority of all cases filed in the country.
Federal courts have a narrower scope. Under 28 U.S.C. § 1331, federal district courts hear civil cases that arise under the Constitution, federal statutes, or treaties.13Office of the Law Revision Counsel. 28 USC 1331 – Federal Question They also hear diversity cases, where the parties are citizens of different states and the amount at stake exceeds $75,000.14Office of the Law Revision Counsel. 28 USC 1332 – Diversity of Citizenship; Amount in Controversy; Costs That dollar threshold keeps smaller disputes out of federal court.
Some conduct violates both systems. A bank robbery can breach both state theft laws and federal statutes, so a defendant may face prosecution in either. The double jeopardy clause does not prevent separate federal and state prosecutions for the same conduct, because the Supreme Court treats the two governments as separate sovereigns.
When federal and state law genuinely conflict, federal law wins under the Supremacy Clause. Congress can preempt state regulation expressly, through regulatory schemes so thorough they leave no room for state rules, or through conflicts that make simultaneous compliance impossible or frustrate what Congress intended.15Congress.gov. Federal Preemption – A Legal Primer Preemption fights come up constantly in immigration, drug regulation, and financial services.
How the Court Tiers Work
Both the federal system and most state systems use three tiers: a trial court, an appeals court, and a court of last resort. Your path through a case depends on which tier it is in, and rulings at each level carry different weight.
Trial Courts
The 94 U.S. District Courts are the trial courts of the federal system.16United States Courts. About U.S. District Courts Every federal case starts there. District courts are the only federal courts where juries hear evidence, witnesses testify, and the factual record is built. Evidence is admitted or excluded under the Federal Rules of Evidence.17United States Courts. Federal Rules of Evidence Parties can file pretrial motions, including a motion for summary judgment asking the court to rule without a trial because the facts are undisputed.18Legal Information Institute. Federal Rules of Civil Procedure Rule 56 – Summary Judgment Criminal defendants can also move to suppress evidence obtained through unconstitutional searches.
Appeals Courts
A party that loses at trial can appeal to one of the 13 U.S. Courts of Appeals. Twelve cover geographic circuits, and the thirteenth, the Federal Circuit, handles specialized matters like patent disputes nationwide.19United States Courts. About the U.S. Courts of Appeals Appeals courts do not retry cases. No juries, no witnesses, no new evidence. A panel of three judges reviews the written record and briefs to decide whether the trial court applied the law correctly. Their decisions bind every district court inside the circuit.
The Supreme Court
The U.S. Supreme Court sits at the top with nine justices who choose almost all of their own cases. A party seeking review files a petition for a writ of certiorari, and at least four justices must vote to accept the case.20Legal Information Institute. Writ of Certiorari The Court typically takes 100 to 150 cases out of more than 7,000 petitions each year, usually to resolve conflicts among the circuits or settle unresolved constitutional questions. A Supreme Court decision is the final word on what the law means, and every court in the country must follow it.
State court systems mostly mirror this three-tier shape, though terminology varies widely. A “superior court” in one state may be a “circuit court” or “district court” in another, and a handful of smaller states skip the intermediate appeals level entirely.21Congress.gov. Federal and State Courts – Structure and Interaction Federal courts process a few hundred thousand cases a year. State courts together process tens of millions.
Civil Cases and Criminal Cases
The system splits proceedings into two broad categories based on who brings the case and what they want. The split changes the rules, the stakes, and the burden of proof.
In a criminal case, the government prosecutes someone accused of an offense against the public. Penalties include fines, probation, imprisonment, and in the most serious state and federal cases, the death penalty. Because a conviction can take away a person’s freedom, the prosecution carries the heaviest burden in the system: it must prove every element of the offense beyond a reasonable doubt, meaning the evidence must leave the jury firmly convinced of guilt.22United States Courts. 3.5 Reasonable Doubt Defined – Model Jury Instructions If reasonable doubt exists, the jury must acquit. This is where the constitutional protections above do most of their work.
A civil case is a dispute between private parties, or between a private party and the government acting outside its criminal role. The usual goal is compensation, not punishment. A plaintiff must prove the claim by a preponderance of the evidence, meaning the claim is more likely true than not.23Legal Information Institute. Preponderance of the Evidence That is a significantly lower bar than beyond a reasonable doubt. Some claims, like fraud, require “clear and convincing evidence,” which falls between the two.
Civil remedies take several forms. Compensatory damages aim to restore the injured party to the financial position they held before the harm. Punitive damages, available in cases of intentional wrongdoing or extreme recklessness, punish the defendant and deter similar conduct. Courts can also issue injunctions ordering someone to stop doing something, or order specific performance requiring a party to fulfill a contract when the subject matter is unique and money would not fairly compensate the loss.
The same conduct can trigger both tracks. Someone who assaults another person may face criminal charges brought by the government and a separate civil suit for damages filed by the victim. The two proceed independently, with different standards of proof and potentially different outcomes.
Settling Disputes Outside Court
Not every legal dispute reaches a judge. Arbitration and mediation resolve a large share of conflicts outside the courtroom, often faster and at lower cost than litigation.
Under the Federal Arbitration Act, a written agreement to arbitrate a dispute arising from a commercial transaction is “valid, irrevocable, and enforceable.”24Office of the Law Revision Counsel. 9 USC 2 – Validity, Irrevocability, and Enforcement of Agreements to Arbitrate Arbitration clauses in employment contracts, consumer agreements, and service terms are binding. If you signed one, a court will generally enforce it and send you to a private arbitrator instead of letting the lawsuit proceed. The arbitrator’s decision is typically final, with very limited grounds for appeal. Courts have enforced these clauses even when they include class-action waivers that stop groups of workers or consumers from bringing collective claims.
Mediation is different. A neutral mediator helps the parties negotiate a resolution but cannot impose a binding outcome. Either side can walk away. Many courts require mediation before a case can go to trial, and it works especially well when the parties have an ongoing relationship they want to preserve.
Deadlines to File
Every legal claim has a filing deadline. Miss it and the court will dismiss the case regardless of its merits. These deadlines, called statutes of limitations, vary dramatically based on the type of claim and whether it falls under federal or state law.
For most federal crimes that are not punishable by death, the default deadline is five years from the date the offense was committed.25Office of the Law Revision Counsel. 18 USC 3282 – Offenses Not Capital Specific federal statutes set longer or shorter windows for particular offenses. On the civil side there is no single federal deadline; it depends on the cause of action, and when a federal statute does not specify, courts often borrow the deadline from the state where the court sits.
State deadlines range from one year to over a decade depending on the claim. Personal injury cases often carry windows of two to four years, while written contract disputes may allow longer. The clock usually starts when the harm occurs or when the injured party reasonably should have discovered it. Courts can sometimes toll the clock, such as when a defendant concealed the wrongdoing or the injured party was a minor. No amount of evidence can revive a claim filed too late, so tracking the deadline is one of the first things to do in any dispute.