Criminal law in the United States comes from five sources stacked in a hierarchy: the U.S. Constitution at the top, then statutes passed by Congress and state legislatures, judicial decisions interpreting those statutes, regulations issued by government agencies, and local ordinances enacted by cities and counties. These are the sources of criminal law a defendant, a prosecutor, or anyone trying to understand a charge will encounter, and each operates at a different level of authority. The Constitution overrides everything else, and most actual criminal offenses — the ones people are charged with every day — are written by state legislatures rather than Congress.
The Constitution Sets the Ceiling
The Constitution itself creates very few criminal offenses. What it does is draw the outer limits that every other criminal law has to respect. A statute, a regulation, or a local ordinance that violates a constitutional protection can be struck down no matter how popular it is or how long it has been on the books.
Several amendments in the Bill of Rights carry most of the weight in criminal cases. The Fourth Amendment protects against unreasonable searches and seizures and generally requires a warrant based on probable cause before police can search a person, home, or belongings.1Congress.gov. Fourth Amendment Evidence obtained through an illegal search is usually inadmissible at trial under the exclusionary rule, which the Supreme Court extended to state prosecutions in Mapp v. Ohio.2Justia Law. Mapp v. Ohio, 367 U.S. 643 (1961)
The Fifth Amendment forbids the government from depriving anyone of life, liberty, or property without due process of law, bars trying a person twice for the same offense, and protects the right to remain silent rather than testify against yourself.3Congress.gov. Overview of Due Process The Sixth Amendment guarantees a speedy and public trial by an impartial jury, notice of the charges, the right to confront witnesses and compel their appearance, and the right to a lawyer — provided at public expense for any felony defendant who cannot afford one, under Gideon v. Wainwright.4Congress.gov. Sixth Amendment The Eighth Amendment prohibits excessive bail, excessive fines, and cruel and unusual punishment, and courts have read it to bar punishments grossly disproportionate to the offense.5Congress.gov. Eighth Amendment
These protections originally restrained only the federal government. The Supreme Court has since held, through a doctrine called selective incorporation, that nearly all of them bind state and local governments through the Fourteenth Amendment’s Due Process Clause.6Congress.gov. Application of the Bill of Rights to the States Through the Fourteenth Amendment That is why a defendant in a state court can invoke the Fourth, Fifth, Sixth, and Eighth Amendments the same way a federal defendant can.
Statutes Are the Main Body of Criminal Law
Statutes passed by legislatures are where almost all criminal offenses actually live. A legislature writes a bill defining the offense, specifying what the government has to prove, and setting a punishment range. If the bill passes and the executive signs it, it becomes binding law.
State Statutes Do Most of the Work
One thing that surprises people is how little of American criminal law is federal. The Tenth Amendment reserves to the states all powers not delegated to the federal government, and the broad authority to protect public safety — the police power — sits with the states.7Congress.gov. State Police Power and Tenth Amendment Jurisprudence State legislatures define and punish assault, robbery, murder, drug possession, and property crimes. Each state writes its own penal code, sets its own sentencing ranges, and funds its own prosecutors, courts, and prisons. The variation is real. An act that counts as a misdemeanor in one state can be a felony in another.
Federal Statutes Have a Narrower Reach
Congress can only create federal crimes tied to its enumerated constitutional powers. The most important of those is the Commerce Clause, which has supported federal statutes on drug trafficking, racketeering, wire fraud, and much more.8Congress.gov. Article I Section 8 Other provisions give Congress authority over counterfeiting, piracy, crimes on federal land, and military justice. Federal criminal offenses are collected primarily in Title 18 of the United States Code.9Office of the Law Revision Counsel. United States Code – Title 18
When Federal and State Law Overlap
The Supremacy Clause in Article VI makes federal law override conflicting state law. If Congress validly uses an enumerated power and a state law directly contradicts the federal statute, the state law is preempted. Courts generally presume Congress does not intend to displace state criminal law in areas states have traditionally regulated, so outright preemption is uncommon. More often, federal and state laws run in parallel, which is why the same conduct — a bank robbery, for example — can produce both federal and state charges.
Judicial Decisions Interpret and Bind
Courts do not write statutes, but their rulings on what statutes mean carry enormous weight. When a judge decides what a vague phrase covers, or whether a given set of facts fits within a statute, that ruling becomes binding precedent for later cases under the doctrine of stare decisis. Lower courts have to follow the interpretations of higher courts in their jurisdiction, which creates predictability across cases.10United States Court of Appeals for the Armed Forces. Digest of Judicial Review and Stare Decisis
The impact goes well beyond defining words. Courts decide whether a confession was coerced, whether a search violated the Fourth Amendment, whether a defense applies, and whether a sentence is proportionate. A Supreme Court decision on any of these questions effectively rewrites the rule for every jurisdiction in the country. If the Court holds that the Eighth Amendment bars a certain sentence, no legislature can bring it back by statute.
What’s Left of Common Law
Early criminal law in England and the colonies was defined entirely by judges through accumulated case decisions rather than legislation. Murder, arson, and robbery were common law crimes. The federal system abandoned common law crimes after the Supreme Court’s 1812 decision in United States v. Hudson, and most states have followed by codifying their offenses in statutes. A handful of states still recognize some common law crimes, but the modern rule is that a crime has to be written in a statute. Common law meanings still matter as an interpretive backdrop: when a statute uses a term like “malice” or “burglary” without defining it, courts often reach for the common law definition.
Administrative Regulations Can Carry Criminal Penalties
Government agencies produce an enormous body of detailed rules on things like pollution, food safety, workplace conditions, and medical devices. Violating some of those rules is a crime, not just a civil infraction, which makes administrative regulations a real source of criminal law.
The Environmental Protection Agency enforces regulations under the Clean Water Act and Clean Air Act. Knowingly discharging pollutants into waterways without a permit carries up to three years in prison per violation, doubling for repeat offenses.11Environmental Protection Agency. Criminal Provisions of Water Pollution Knowing violations of Clean Air Act standards for hazardous pollutants can bring up to five years, and releasing hazardous substances in a way that knowingly endangers human life can bring up to fifteen.12Environmental Protection Agency. Criminal Provisions of the Clean Air Act The FDA has its own criminal investigation office for food, drug, and medical device violations, including counterfeit drugs and contaminated food.13Food and Drug Administration. Criminal Investigations OSHA enforces workplace safety standards, and an employer whose willful violation causes a worker’s death faces up to six months in prison and a fine of up to $10,000 for a first offense, with those penalties doubling on a second conviction.14Occupational Safety and Health Administration. 29 U.S.C. 666 – Penalties
Agencies cannot invent criminal offenses on their own. The Supreme Court has held that only Congress can declare conduct criminal. When Congress authorizes an agency to write regulations, violations can carry criminal penalties only if the underlying statute explicitly makes regulatory violations a crime, Congress sets the punishment, and the regulation stays within the statute’s scope.15Congress.gov. Criminal Statutes and Nondelegation Doctrine A regulation that reaches further than the statute allows cannot carry criminal weight, and that boundary is where many regulatory enforcement challenges end up being fought.
Local Ordinances
Cities and counties also create rules that carry criminal or quasi-criminal penalties, but their authority is far narrower than a state legislature’s. Local ordinances typically cover noise, public nuisance, code enforcement, zoning, and minor public-order offenses. Penalties are usually limited to fines and, in some cases, short jail terms for misdemeanor-level violations. A city cannot create a felony or impose a penalty beyond what state law permits, and a local ordinance that conflicts with state law is normally void. How much a locality can do depends on what the state constitution and enabling statutes authorize.
How the Sources Work Together
In practice these sources overlap constantly. A state legislature writes a fraud statute. An appellate court interprets a disputed term in that statute, and the interpretation binds every lower court in the state. A defendant argues the statute violates the First Amendment, and a court either upholds it or strikes it down against the Constitution. At the same time, a federal agency may have fraud-related regulations with their own criminal penalties, authorized by a federal statute grounded in the Commerce Clause.
The hierarchy is clean on paper. The Constitution overrides everything. Federal statutes, within their proper scope, override conflicting state laws. State statutes override conflicting local ordinances. Court interpretations of each of those sources bind later courts in the same jurisdiction. A single act can violate a local ordinance, a state statute, and a federal regulation at the same time, each rooted in a different source and prosecuted by a different set of lawyers. That layered structure is what makes the American criminal justice system both powerful and complicated.