There is no single official count of the types of law in the United States, because the usual labels describe the same rules from different angles. Legal professionals generally work with about seven broad categories: public law, private law, statutory law, common law, substantive law, procedural law, and the split between federal and state systems. Specialized bodies — military, tribal, international, and maritime law — sit alongside those groupings. A single lawsuit can carry several labels at once without contradiction.
Public Law and Private Law
The first split is about who is on the other side of the dispute. Public law covers the relationship between people and the government. Private law covers disputes between individuals, businesses, and other non-government parties, where the government just supplies the courthouse.
Public law has three main branches. Constitutional law draws from the U.S. Constitution and its amendments to define the structure of government and protect individual rights such as free speech, due process, and equal protection. Administrative law governs how federal agencies write and enforce regulations; before adopting a rule, an agency generally must publish a notice of proposed rulemaking in the Federal Register, cite its legal authority, and take public comments.1Office of the Law Revision Counsel. 5 USC 553 – Rule Making Properly adopted regulations in the Code of Federal Regulations carry the same legal weight as an act of Congress.2Congress.gov. An Overview of Federal Regulations and the Rulemaking Process Criminal law is the third branch, treated as public law because a crime is an offense against society, not just the victim. Federal offenses are organized in Title 18 and range from minor infractions of five days or less up through Class A felonies carrying life imprisonment.3Office of the Law Revision Counsel. 18 USC 3559 – Sentencing Classification of Offenses Because the consequences are so severe, criminal cases require the highest standard of proof: beyond a reasonable doubt.
Private law is where most everyday legal life happens. Contract law handles agreements and what happens when someone breaks one; the usual remedy is money damages, though a court may order the breaching party to actually perform the promise when the subject is unique, like a specific piece of real estate. Tort law covers injuries caused by negligence, recklessness, or intentional wrongdoing outside a contract, from car accidents to medical malpractice, with the goal of making the injured person whole. Property law covers ownership and its transfer, including real estate and intellectual property. Family law covers marriage, divorce, custody, and support. Because the government isn’t seeking to imprison anyone, the standard of proof is lower: a preponderance of the evidence, meaning more likely than not. Most private-law disputes settle before trial.
Statutory Law and Common Law
This split answers a different question: where does the rule come from? Statutory law is written by legislatures. Congress passes federal statutes, state legislatures pass state statutes, and city councils pass ordinances. When a statute conflicts with a court-made rule, the statute wins.
Common law is built from judicial decisions. When a court resolves a case and explains its reasoning, that decision becomes precedent for future courts under the principle of stare decisis, meaning “stand by the decision.”4Federal Judicial Center. Stare Decisis Only the court’s actual holding — the legal rule needed to decide the case — binds later courts. The rest of the opinion is commentary.
Most legal questions involve both sources. A legislature writes a statute and courts interpret it through decisions that fill in the gaps. Whole areas, like negligence, grew almost entirely through case law before legislatures started codifying pieces of them. Forty-nine states follow this common-law tradition. Louisiana is the exception: its private law comes from a civil-law tradition rooted in French and Spanish codes, where the written code takes priority over judicial precedent rather than the other way around.
Substantive Law and Procedural Law
Substantive law defines your actual rights and obligations. It tells you what counts as breach of contract, what behavior qualifies as negligence, and what elements a prosecutor has to prove for a particular crime. These rules come from both statutes and case law, and they are what judges and juries apply to the facts.
Procedural law is the machinery that moves a case through the system: how lawsuits are filed, how evidence is exchanged, how trials run, how appeals work. The Federal Rules of Civil Procedure govern civil cases in federal court.5Legal Information Institute. Federal Rules of Civil Procedure Rule 12 – Defenses and Objections The Federal Rules of Criminal Procedure separately govern arrests, charging, and criminal trials.6Legal Information Institute. Federal Rules of Criminal Procedure
Procedure gets less attention than substance, but it can decide a case on its own. Missing a filing deadline, serving papers incorrectly, or blowing a statute of limitations can end the case before anyone looks at the merits. A tort claim against the United States, for example, is permanently barred unless the injured party first files in writing with the appropriate agency within two years.7Office of the Law Revision Counsel. 28 USC 2401 – Time for Commencing Action Against United States
Federal Law and State Law
The country runs on a dual legal system. Federal law covers matters of national scope: immigration, bankruptcy, interstate commerce, and crimes like drug trafficking or tax evasion. Congress has particularly broad authority over immigration, long recognized by the Supreme Court as a plenary federal power.8Constitution Annotated. Overview of Congress’s Immigration Powers When federal and state law conflict, the Supremacy Clause in Article VI makes federal law control.9Congress.gov. Constitution of the United States – Article VI
State law handles most day-to-day legal life: family disputes, property transactions, contracts, personal injury, and the vast majority of criminal prosecutions. Each state has its own constitution, legislature, and courts, so penalties for a common crime like theft and requirements for something like a marriage license can look very different from state to state.
The systems overlap constantly. Selling illegal drugs, for instance, can violate both federal and state law, leading to prosecution in either or both systems. When a case involves parties from different states or raises a federal question, it may qualify for federal court even if it could also be heard in state court. That concurrent jurisdiction gives plaintiffs a choice of forum in many situations.10Constitution Annotated. Article III Section 2
Military Law and Tribal Law
Two systems operate largely outside the civilian federal-state framework.
Military law comes from the Uniform Code of Military Justice. It applies to active-duty service members, certain reservists, military retirees receiving pay, cadets, and prisoners of war. The UCMJ covers offenses that are also civilian crimes, like assault, theft, and fraud, as well as offenses unique to the armed forces, like desertion, insubordination, and conduct unbecoming an officer.11Office of the Law Revision Counsel. 10 USC 802 – Art. 2. Persons Subject to This Chapter Military courts have worldwide jurisdiction, and the offense does not have to be connected to the service member’s duties. Civilians accompanying the armed forces in the field during a declared war or contingency operation can also fall under the UCMJ.
Tribal law flows from the inherent sovereignty of federally recognized tribes. Tribes have the authority to make and enforce their own civil and criminal laws, run court systems, tax within their jurisdiction, and determine tribal membership.12Bureau of Indian Affairs. Frequently Asked Questions Executive, legislative, and judicial powers of self-government are recognized in federal statute.13Office of the Law Revision Counsel. 25 USC 1301 – Definitions Tribal sovereignty is limited by treaties, acts of Congress, and federal court decisions, but what remains is protected from encroachment by state governments. Criminal enforcement on tribal lands is one of the most complicated jurisdictional areas in American law.
International Law and Maritime Law
International law governs relationships between nations rather than between individuals. It draws from two main sources: treaties, which are formal written agreements between countries, and customary international law, which arises from long-standing practices nations follow out of a sense of legal obligation. The International Court of Justice hears disputes between UN member states, though enforcement depends on the willingness of sovereign nations to comply.
Maritime law, also called admiralty law, is a specialized body of rules covering navigation, shipping, waterway commerce, and injuries at sea. Federal district courts hold exclusive jurisdiction over admiralty cases, including seizure of vessels to enforce maritime liens and prize cases involving property captured during wartime.14Office of the Law Revision Counsel. 28 USC 1333 – Admiralty, Maritime, and Prize Cases The Constitution extends federal judicial power to “all Cases of admiralty and maritime Jurisdiction,” making this one of the oldest recognized areas of federal authority.10Constitution Annotated. Article III Section 2 State courts can hear some overlapping maritime claims when a plaintiff seeks ordinary money damages, but actions against a vessel itself must go through federal court.15Constitution Annotated. Overview of Admiralty and Maritime Jurisdiction
Why the Categories Overlap
These labels cut across each other, which is why there is no clean count. A wrongful death lawsuit filed in state court is simultaneously private law (dispute between individuals), civil law (not criminal), substantive law (defining the right to sue over a death caused by negligence), procedural law (governing deadlines and trial rules), and state law (applying that state’s wrongful death statute). All five labels are correct; they answer different questions about the same case.
To figure out which rules apply to a specific situation, start with jurisdiction and subject matter. Is the case federal or state? Criminal or civil? From there, the substantive rules tell you what rights and obligations are at stake, and the procedural rules tell you how to enforce them. The categories are a map, not a set of rigid boxes, and the same case will usually sit on more than one part of the map at once.