Where do you look to see if something you want to do violates some criminal law? The answer is “in many places.” Criminal law originates from many sources. Some criminal law is the result of constitutional conventions, so you would need to review federal and state constitutions. Other criminal laws result from the legislative or initiative process, so you will need to review state statutes or congressional acts. Moreover, some criminal law results from the work of administrative agencies, so you need to review state and federal administrative rules. Finally, criminal law that emerges from “case law” originates from appellate court opinions written by judges. These court opinions, called “decisions,” are published in both official and unofficial reports (but thanks to the internet, they are now easy to find if you know the parties’ names). Much of our criminal law descended from the English common law. This law developed over time, through custom and tradition, and it is a bit more difficult to locate, but it is mentioned in treatises and legal “hornbooks” (like legal encyclopedias) and is often referred to in case decisions.
The Federal Constitution—The Constitution of the United States
Although the United States Constitution recognizes only three crimes (counterfeiting, piracy, and treason), it nevertheless plays a significant role in the American criminal justice system. Most importantly, the Constitution establishes limits on certain types of legislation or substantive law, and it provides significant procedural constraints on the government when it seeks to prosecute individuals for crimes. The Constitution also establishes federalism (the relationship between the federal government and state governments), requires the separation of powers between the three branches of government (the judicial branch, the legislative branch, and the executive branch), and limits Congress’s authority to pass laws not directly related to either its enumerated powers (listed in the Constitution) or implied powers (inferred because they intertwined with the enumerated powers).
U.S. Constitutional Limitations on Criminal Law and Procedure
The drafters of the federal Constitution were so concerned about two historic cases of abuse by English Parliament (ex post facto laws and bills of attainder) that they prohibited Congress from passing these types of laws in the original body of the Constitution. (See, Article I Section 9 of the Constitution.) Ex post facto laws are laws that are retroactively applied, or punishments retroactively increased, or changes in the amount and types of evidence that is required of the government in order to successfully prosecute an individual. Bills of attainders are laws that are directed at a named individual or group of individuals and has the effect of declaring them guilty without a trial.
Most of the other limitations are found within the Bill of Rights, the first ten amendments to the U.S. Constitution. The states adopted the Bill of Rights in 1791. The statesmen had opposing viewpoints concerning how strong the national government should be and how strong state governments should be. Even as the original federal constitution was being circulated and ratified, the framers were thinking about the provisions that became known as the Bill of Rights.
The First Amendment limits Congress’s ability to pass laws that limit free speech, freedom of religion, freedom of assembly and association. The Second Amendment limits Congress’s ability to outlaw the personal possession of firearms. The Fourth, Fifth, Sixth and Eighth Amendments have provisions that govern criminal procedure during the investigative, pretrial, and trial phases. The Eighth Amendment sets limits on the government’s ability to impose certain types of punishments, impose excessive fines, and set excessive bail. The Due Process Clauses of the Fifth and Fourteenth Amendment require that criminal justice procedures be fundamentally fair. The Fourteenth Amendment’s Equal Protection Clause requires that, at a minimum, there be some rational reason for treating people differently, by law. For example, states can pass laws prohibiting minors from purchasing and consuming alcohol because states have a reasonable interest in protecting the health and welfare of its citizens. More generally, the principle of substantive due process requires that any law prohibiting certain behaviors be based in the public interest, or reflect a well-evidenced problem. The limitations on government behavior applied by each of these amendments are discussed in further detail below. Overall, the impact of the Bill of Rights was to place substantial checks on the federal government’s ability to define, and prosecute, crimes.
The Incorporation Debate
When drafted and passed, the U.S. Constitution and the Bill of Rights applied only to the federal government. Individual states each had their own guarantees and protections of individuals’ rights found in the state constitutions. (See below.) Since 1868, the Fourteenth Amendment has become an important tool for making states also follow the provisions of the Bill of the Rights. It was drafted to enforce the Civil Rights Act passed in 1866 after the Civil War, given the recalcitrance of state in the former Confederacy. Section 1 of the Fourteenth Amendment prohibits the states from depriving any person of life, liberty, or property, without due process of law. It prohibits states from adopting any laws that abridge the privileges and immunities of the citizens of the United States and requires that states not deny any person equal protection under the law (U.S. Const. amend. XIV, § 2).
The practice of making the states follow provisions of the Bill of Rights is known as incorporation. Over decades, the Supreme Court debated whether the Bill of Rights should be incorporated all together, in one-fell-swoop, called total incorporation, or piece-by-piece, called selective incorporation. The case-by-case, bit-by-bit approach won. In a series of decisions, the Supreme Court has held that the Due Process Clause of the Fourteenth Amendment makes enforceable against the states those provisions of the Bill of Rights that are “implicit in the concept of ordered liberty.”  For example, in 1925 the Court recognized that the First Amendment protections of free speech and free press apply to states as well as to the federal government.  In the 1960s, the Court selectively incorporated many of the procedural guarantees of the Bill of Rights. The Court also used the Fourteenth Amendment to extend substantive guarantees of the Bill of Rights to the states.
In the News
The most recent example of “incorporation” occurred on February 20th, 2019, when the U.S. Supreme Court incorporated the right to be free from excessive fines found in the Eighth Amendment. Interestingly, the case that led to this landmark ruling, Timbs v. Indiana, hinged on the state of Indiana’s seizure of the appellant’s (Tyson Timbs’) $42,000 Land Rover SUV. Read more here.
Limitations Found in the “Penumbra” of the Constitution
Sometimes the Constitution doesn’t explicitly state protection or right that the courts have nevertheless found to be inherent or found within the Constitution. Justice Douglas, writing the majority opinion in Griswold v. Connecticut, 381 U.S. 479 (1965), stated
“[The] . . . specific guarantees in the Bill of Rights have penumbras, formed by emanations from those guarantees that help give them life and substance. … Various guarantees create zones of privacy. The right of association contained in the penumbra of the First Amendment is one, as we have seen. The Third Amendment in its prohibition against the quartering of soldiers ‘in any house’ in time of peace without the consent of the owner is another facet of that privacy. The Fourth Amendment explicitly affirms the ‘right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.’ The Fifth Amendment in its Self-Incrimination Clause enables the citizen to create a zone of privacy which government may not force him to surrender to his detriment. The Ninth Amendment provides: ‘The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.’
The Fourth and Fifth Amendments were described … as protection against all governmental invasions ‘of the sanctity of a man’s home and the privacies of life.’ We recently referred in Mapp v. Ohio, 367 U. S. 643, 656, to the Fourth Amendment as creating a ‘right to privacy, no less important than any other right carefully and particularly reserved to the people.’ (Footnote omitted).” 381 U.S. at 484-485.
For the past 57 years, legislatures were effectively prohibited from making laws that allow the government to invade people’s privacy, even though no specific amendment can be pointed to. In fact, from 1965 to 2015, the Supreme Court decided many landmark cases that referenced the right to privacy. Specifically, the Court found the right to privacy in the context of reproductive freedom (See, e.g., Roe v. Wade, 410 U.S. 113 (1972) (right to abortion), Eisenstadt v. Baird, 405 U.S. 438 (1972) (the right of married persons to possess contraceptives), Griswold v. Connecticut, 381 U.S. 479 (1965) (declaring invalid the ban on contraceptives), Stanley v. Georgia, 394 U.S. 557 (1969) (the right to view and possess adult pornography), and the right of adults to engage in consensual sexual contact), and Lawrence v. Texas, 539 U.S. 558 (2003) (the right of adults to engage in consensual sexual contact)). The right to privacy also supported the Court’s decision in Obergefell v. Hodges (2015), which required states to license and recognize same-sex marriages.
However, the existence of a Constitutional right to privacy suffered a dramatic setback in June 2022, when the Supreme Court overturned its own precedent in Roe v. Wade (1972), deciding that the state of Mississippi could restrict access to abortion. While the written decision in Dobbs v. Jackson Women’s Health Organization (2022) claims that other freedoms underwritten by the right to privacy (such as same-sex marriage, interracial marriage, and access to contraception) were not at risk, legal scholars generally agree that these guarantees may also be subject to judicial revision.
States’ constitutions, similar to the federal constitution, set forth the general organization of state government and basic standards governing the use of governmental authority. Although the federal constitution is preeminent because of the Supremacy Clause, state constitutions are still significant. State constitutional rules are supreme as compared to any other rules coming from all other state legal sources (statutes, ordinances, administrative rules) and prevail over such laws in cases of conflict. The federal constitution sets the floor of individual rights, but states are free to provide more individual freedoms and protections that are granted by the federal constitution. State constitutions are defined and interpreted by state courts, and even identical provisions in both the state and federal constitution may be interpreted differently. For example, a state constitution’s guarantee to be free from unreasonable searches and seizures may mean that, under state law, roadblocks established to identify impaired, intoxicated drivers are impermissible, but under the federal constitution, these roadblocks are permitted and are not deemed to be unreasonable seizures.
Rule of Law, Constitutions and Judicial Review
One of the key features of the American legal system has been its commitment to the rule of law. Rule of law has been defined as a “belief that an orderly society must be governed by established principles and known standards that are uniformly and fairly applied.”  Reichel identified a three-step process by which countries can achieve rule of law.  The first step is that a country must identify core, fundamental values. The second step is for the values to be reduced to writing and written somewhere that people can point to them. The final step is to establish a process or mechanism whereby laws or governmental actions are tested to see if they are consistent with the fundamental values. When laws or actions embrace the fundamental values, they are considered valid, and when the laws or actions conflict with the fundamental values, they are invalid.
Applying this three-step process to America’s approach to law, one can see that Americans have recognized fundamental values, such as the right to freedom of speech, the right to privacy, and the right to assemble. Second, we have reduced these fundamental values to writing and, for the most part, have compiled them in our constitutions (both federal and state). Third, we have a mechanism, that of judicial review, by which we judge whether our laws and our government actions comply with or violate our fundamental values found within our constitutions. Judicial review is the authority of the courts to determine whether a law (a legislative action) or action (an executive or judicial action) conflicts with the Constitution. Judicial review can be traced to the case of Marbury v. Madison, 5 U.S. 137 (1803), in which Chief Justice John Marshall wrote, “It is emphatically the province and duty of the judicial department to say what the law is. Those who apply the rule to particular cases, must of necessity expound and interpret that rule. If two laws conflict with each other, the courts must decide on the operation of each.”