How the U.S. Legal System Works

The United States doesn't have one legal system — it has fifty-two, running in parallel: a federal system, fifty state systems, and the District of Columbia, plus thousands of local governments layered on top. Understanding how they fit together is the foundation for understanding almost any specific legal topic, from a divorce to a criminal charge to a business dispute. This guide is a general orientation to that structure — the sources of law, the courts, the people who staff them, and how a matter moves through the system. It is educational information, not legal advice.

Overview: A System of Systems

At the broadest level, the U.S. legal system is built on federalism: a national government with defined, limited powers, and separate state governments that retain broad authority over most day-to-day legal matters — including family law, most criminal law, contracts, property, and personal injury. Local governments (counties, cities, and towns) add another layer, regulating things like zoning, building codes, and local licensing. A single set of facts — say, a car accident — can potentially touch state traffic law, state tort law, a local ordinance, and, in some circumstances, federal law, all at once.

Sources of Law

Four broad categories make up "the law" in any American jurisdiction:

• Constitutions — the U.S. Constitution at the federal level, and each state's own constitution, both of which sit above ordinary statutes and limit what legislatures and other government actors can do.
• Statutes — laws passed by a legislature (Congress at the federal level, state legislatures at the state level), organized into codes like the United States Code or a state's own code.
• Regulations — detailed rules issued by administrative agencies under authority delegated to them by statute (for example, federal regulations are compiled in the Code of Federal Regulations).
• Case law — published court decisions that interpret constitutions, statutes, and regulations, and that establish binding precedent within their jurisdiction.

Federal Law

Federal law applies nationwide but only within the areas the Constitution assigns to the federal government — things like interstate commerce, immigration, federal taxation, bankruptcy, patents and copyrights, and federal crimes. Congress creates federal statutes; federal agencies (like the EPA or the SEC) issue regulations implementing those statutes; and federal courts interpret and apply both. Our companion guide on the Constitution and how federal laws are made walks through that process in detail.

State Law

Each state has its own constitution, legislature, statutes, regulations, and court system, and states retain broad authority over subjects the Constitution doesn't assign to the federal government — most family law (including divorce, discussed in our guides to divorce law in Maryland and how divorce works across the U.S.), most criminal law, contract and property law, and most personal injury law. This is why the specific legal rule for something as common as divorce or a traffic violation depends heavily on which state you're in.

Local Law

Below the state level, counties, cities, and towns can pass ordinances — local laws covering things like zoning, noise, building and fire codes, business licensing, and local traffic rules — under authority delegated to them by the state. Local law generally can't conflict with state law; where it does, state law controls.

How Laws Are Created

Statutes are created through each jurisdiction's legislative process — Congress at the federal level (see our detailed walkthrough of how a bill becomes federal law), and a state legislature for state law, generally following a similar pattern of introduction, committee review, floor votes in each chamber, and the executive's signature or veto. Regulations, by contrast, are created by administrative agencies through a rulemaking process — typically involving a proposed rule, a public comment period, and a final rule — under authority a legislature has delegated to the agency by statute.

How Courts Interpret Laws

Courts don't just apply the literal words of a statute in isolation — they interpret it, often relying on the statute's text, structure, legislative history, and prior court decisions interpreting similar language. Once a court issues a published decision, that ruling generally becomes precedent: future courts within the same jurisdiction (and lower courts within that court's authority) are expected to follow it under the principle of stare decisis ("to stand by things decided"), unless a higher court overturns it or a later case is meaningfully different on the facts.

The Court Structure

Federal Courts

The federal court system has three main levels: 94 U.S. district courts (the federal trial courts, where federal cases are first filed and decided), 13 U.S. courts of appeals (which review district court decisions for legal error), and the U.S. Supreme Court (the court of last resort for federal constitutional and statutory questions). Federal courts are courts of limited jurisdiction — they can only hear cases the Constitution or a federal statute authorizes them to hear, generally cases involving a federal question or, in some circumstances, cases between citizens of different states.

State Courts

Every state has its own court system, generally structured similarly to the federal system: trial courts (where cases are first filed, and where witnesses testify and evidence is presented), one or more levels of appellate courts, and a state supreme court (sometimes called by a different name, like New York's Court of Appeals) as the final word on state law. Unlike federal courts, state courts are courts of general jurisdiction — they can hear nearly any type of case, including most federal claims, except in the narrow areas where federal law gives federal courts exclusive jurisdiction.

Tribal and Territorial Courts

Beyond the federal and state systems, the U.S. includes additional court systems that operate under their own rules. Federally recognized Native American tribes generally have inherent authority to maintain their own tribal courts, which apply tribal law (and, in some circumstances, federal law) within the tribe's jurisdiction, subject to specific federal statutes that define the boundaries between tribal, state, and federal authority. Separately, U.S. territories — including Puerto Rico, Guam, the U.S. Virgin Islands, American Samoa, and the Northern Mariana Islands — maintain their own local court systems, alongside federal district courts that sit in several of the territories. These systems add real complexity to "the U.S. legal system" beyond the federal/state split most overviews focus on.

Jurisdiction: Federal Versus State

Jurisdiction is a court's legal authority to hear a particular case. Some matters — most federal crimes, bankruptcy, patents — fall under the exclusive jurisdiction of federal courts. Others fall entirely within state authority, like most divorces, wills, and routine criminal cases. Still others can be brought in either federal or state court depending on the circumstances, such as a case that raises a federal legal question or a state-law dispute between citizens of different states above a certain dollar amount (diversity jurisdiction). Figuring out which court has authority over a given case is often one of the first legal questions in any dispute.

Judges

Judges preside over cases, decide legal questions, and (in cases without a jury) can also decide the facts. Federal judges — including Supreme Court justices — are nominated by the President and confirmed by the Senate, and Article III judges serve for life absent impeachment, which is intended to insulate them from political pressure. State judges are selected differently depending on the state: some are elected, some are appointed by the governor, and some go through a hybrid process, often followed by periodic retention elections.

Juries

In many civil and most serious criminal cases, the Constitution guarantees a right to a jury — a group of citizens who hear the evidence and decide factual questions, such as whether a defendant is liable or guilty, applying the law as the judge instructs them. Not every case involves a jury: many civil cases (including most divorces) are decided by a judge alone, either because no jury right applies or because the parties waive it.

Attorneys

Attorneys represent parties in legal proceedings, advise clients on their rights and options, and are licensed and regulated on a state-by-state basis (each state sets its own bar admission requirements and ethical rules). An attorney's role varies with the type of case — negotiating, drafting documents, arguing motions, and, when necessary, presenting a case at trial.

Prosecutors

In criminal cases, the government is represented by a prosecutor — a U.S. Attorney's office for federal crimes, or a district attorney, state's attorney, or similarly titled state/local official for state and local crimes. Prosecutors decide whether to bring charges, what charges to bring, and represent the government (not the crime victim personally) throughout the case.

Government Agencies

Administrative agencies — at the federal level (like the IRS, FDA, or SEC) and the state level (like a state's motor vehicle or licensing agency) — create regulations, enforce them, and often resolve disputes through their own internal administrative processes before (or sometimes instead of) a case ever reaches a traditional court.

Civil Cases

Civil cases resolve disputes between private parties (individuals, businesses, or government entities acting in a civil capacity) over things like contracts, property, personal injury, and family law matters such as divorce. The party bringing the case (the plaintiff) generally must prove their claim by a "preponderance of the evidence" — meaning more likely than not — a lower standard than in criminal cases. Remedies in civil cases typically include money damages, injunctions (court orders to do or stop doing something), or a formal legal status change, such as a divorce decree.

Criminal Cases

Criminal cases are brought by the government against a person accused of violating a criminal statute, and can result in penalties including fines, probation, or incarceration. Because the stakes are higher, criminal defendants have specific constitutional protections not guaranteed in civil cases — including the right to counsel, the right against self-incrimination, and the right to a jury trial for most serious offenses — and the government must prove guilt "beyond a reasonable doubt," a substantially higher standard than in civil cases.

Administrative Proceedings

Many disputes involving a government agency — a denied benefits claim, a licensing dispute, an immigration matter — are resolved first (and sometimes exclusively) through administrative proceedings before the agency itself, often in front of an administrative law judge, rather than in a traditional trial court. These proceedings have their own procedural rules, and a party who loses at the agency level can often, but not always, seek further review in a regular court.

Alternative Dispute Resolution

Not every civil dispute is resolved through a courtroom trial. Arbitration — where the parties present their case to a private arbitrator (or panel) whose decision is typically binding — and mediation — where a neutral third party helps the parties negotiate their own resolution rather than imposing one — are both widely used across the country, sometimes because a contract requires it and sometimes because the parties or the court prefer it to a full trial. Many state courts actively encourage or require mediation for certain case types, including family law disputes, before a case can proceed to trial.

Appeals

A party who believes the trial court (or, in an administrative matter, the agency) made a legal error can generally appeal to a higher court. Appellate courts don't retry the facts or hear new evidence — they review whether the law was correctly applied based on the existing trial record — and can affirm, reverse, or send the case back (remand) for further proceedings.

Basic Legal Research Concepts

Finding "the law" on a given topic usually means looking in one or more of a few places: the relevant constitution, the applicable statute (in a federal or state code), any regulations implementing that statute, and case law interpreting all of the above. Free official resources — like Congress.gov and the National Archives at the federal level, and a state's official legislature or courts website at the state level — are generally the most reliable and current starting points, since commercial or informal sources can be outdated or state-specific rules can be presented as if they were nationwide.

How the Pieces Fit Together

A single legal issue often moves through several of these layers at once. Take a divorce: it's filed in a state trial court, decided under that state's family law statutes and case law, and, if a party disagrees with the outcome, reviewed by that state's appellate courts — with federal law appearing only at the margins, for issues like the tax treatment of alimony or dividing a federally regulated retirement account. Understanding which layer governs which part of a legal question is often the key to understanding the issue itself, whether it's how a divorce actually proceeds, Maryland's specific divorce rules, or a broader civics question like how many laws exist in the U.S.