Administrative Law (Agency-Made Law)
State and federal legislatures cannot keep up with the task of enacting legislation on all the myriad subjects that must be regulated by law. In each branch of government, various administrative agencies exist with authority to create administrative law. At the federal level, for example, the Environmental Protection Agency enacts regulations against environmental crimes. At the state level, the Department of Motor Vehicles enacts laws concerning drivers’ license suspension. Administrative regulations are enforceable by the courts provided that the agency has acted within the scope of its delegated authority from the legislature.
One important source of criminal law in the United States is common law. English law developed over centuries and, generally, when we refer to American common law, we are referring to the common law rules brought over from England to the United States when we became a nation. However, this is not necessarily always clear.  LaFave describes the process by which common law was derived in England:
“. . . Although there were some early criminal statutes [in England], in the main the criminal law was originally common law. Thus by the 1600s, the judges, not the legislature, had created and defined the felonies of murder, suicide, manslaughter, burglary, arson, robbery, larceny, rape, sodomy and mayhem; and such misdemeanors as assault, battery, false imprisonment, libel, perjury, and intimidation of jurors. During the period from 1660 . . . to 1860 the process continued with the judges creating new crimes when the need arose and punishing those who committed them: blasphemy (1676), conspiracy (1664), sedition (18th century), forgery (1727), attempt (1784), solicitation (1801). From time to time the judges, when creating new misdemeanors, spoke of the court’s power to declare criminal any conduct tending to “outrage decency” or “corrupt public morals,” or to punish conduct contra bonos mores. Thus, they found “running naked in the streets”, “publishing an obscene book”, and “grave-snatching” to be common law crimes.
Common law is a source of both substantive and procedural law (discussed below), but it is important to note that there are no federal common law crimes. If Congress has not enacted legislation to make certain conduct criminal, that conduct cannot constitute a federal crime. Moreover, common law only stands where there exists no statutory (or legislative) law, and common law standards are always displaced by new legislative enactments. Finally, common law is subject to the same limitations posed by federal and state constitutions.
Judge-Made Law: Case Law
The term case law refers to legal rules announced in opinions written by appellate judges when deciding appellate cases before them. Judicial decisions reflect the court’s interpretation of constitutions, statutes, common law, or administrative regulations. When the court interprets a statute, the statute, as well as its interpretation, control how the law will be enforced and applied in the future. The same is true when a court interprets federal and state constitutions. When deciding cases and interpreting the law, judges are bound by precedent.
Stare Decisis and Precedent: Been There, Done (must do) That.
The doctrine of stare decisis comes from a Latin phrase that states, “to stand by the decisions and not disturb settled points”. It tells the court that if the decisions in the past have held that a particular rule governs a certain fact situation, that rule should govern all later cases presenting the same fact situation. Under the doctrine of stare decisis, past appellate court decisions form precedent that judges must follow in similar subsequent cases. Stare decisis permits society to presume that bedrock principles are founded in the law rather than in the proclivities of individuals, and thereby contribute to the integrity of our constitutional system of government, both in appearance and fact.  Trial courts and appellate courts must follow the controlling case law that has already been announced in appellate court decisions from their own jurisdiction. Trial courts must follow precedent when they decide questions of law. [Questions of law include what a statute means, what the law states, how the constitution should be interpreted, whether a particular law even applies under the facts in the case before them. On the other hand, questions of fact are decided by jurors (or judges in bench trials) and include, for example, how fast was the defendant driving, what color hat the defendant was wearing, or whether the gun went off accidentally.] One way courts get around precedent is to distinguish the facts in the case before them as much different than the facts in the earlier case. For example, if the court decides that the fact that the defendant was running away from the scene, in this case, is so different from the earlier case in which the defendant was merely walking away from the scene, then there is no precedent it must follow.
The advantages of stare decisis include efficiency, equality, predictability, the wisdom of past experience, and the image of limited authority.  Efficiency occurs because each trial judge and the appellate judge does not have to work out a solution to every legal question. Equality results when one rule of law is applied to all persons in the same setting. “Identical cases brought before different judges should, to the extent humanly possible, produce identical results. … Stare decisis assists in providing uniform standards of law for similar cases decided in the same state. It provides a common grounding used by all judges throughout the jurisdiction.”  Stare decisis provides stability in allowing individuals to count on the rules of law that have been applied in the past.
In the federal system, all federal courts must follow the decisions of the Supreme Court,fdc as it is the final interpreter of the federal constitution and federal statutes. If, however, the Supreme Court has not ruled on an issue, then the federal trial courts (U.S. District Courts and U.S. Magistrate Courts) and federal appellate courts (Circuit Courts of Appeals) must follow decisions from their own circuit. Each circuit is treated, in effect, as its own jurisdiction, and the court of appeals for the various circuits are free to disagree with each other.
Because stare decisis is not an absolute rule, courts may reject precedent by overruling earlier decisions. One factor that courts will consider before overruling earlier case law is the strength of the precedent. Another factor is the field of law involved. Courts seem to be more reluctant to override precedents governing property or trade where commercial enterprises are more likely to have relied quite heavily on the precedent. The most compelling basis upon which a court will overturn precedent, however, is if it perceives the presence or absence of changed circumstances. For example, scientific or technological developments may warrant the application of new rules. Consider the common law year and a day rule which required the government, in a murder prosecution, to prove that the victim died within one year and a day of the attack. The rule is premised on the idea that there needed to be some showing that the defendant’s act caused the death. Medical science now makes it possible to trace the source of fatal blow, so murder statutes no longer include the year and a day rule. (More recently, the Court considered whether the social and economic opportunity enjoyed by women had significantly improved since the 1972 decision in Roe v. Wade, and in turn, whether the constitutional protection of abortion was warranted.) One final ground for overruling a prior decision is general changes in the spirit of the times. For example, in Trop v. Dulles, 356 U.S. 86 (1958), the Court looked to “evolving standards of decency” in deciding whether the defendant’s punishment was cruel and unusual and thus violated the Eighth Amendment.
Court Rules of Procedure
The U.S. Supreme Court and state supreme courts make laws that regulate the procedures followed in the lower courts- both appellate and trial courts- in that jurisdiction. These court rules, adopted by the courts to facilitate the administration and processing of cases, are generally limited in scope, but they may nevertheless provide significant rights for the defendant. For example, the rules governing speedy trials may be governed generally by the Constitution, but very specifically by court rules in a particular jurisdiction.
Local courts may also pass local court rules that govern the day-to-day practice of law in these lower courts. For example, a local court rule may dictate when and how cases are to be filed in that jurisdiction. Generally, the local bar (all the attorneys in the jurisdiction) are consulted, and a workgroup consisting of judges, trial court administrators, and representatives from the district attorney’s office, the public defender’s office, assigned counsel consortiums, and private attorneys will meet every few years to decide on the local rules.
Okay, so where do I look to see if my behavior is prohibited?
Because criminal law has many sources–constitutions, legislative enactments, administrative rules, case law, and common law–it is not necessarily an easy task to determine whether your behavior or the way government responds to your behavior, is lawful. First, it is always advisable to know your rights under the federal constitution and your state constitution and understand what limits the constitution places on legislative enactments and law enforcement actions. Still, even assuming that laws have been properly enacted and that police have followed proper procedure, it may be difficult to determine whether your behavior is prohibited. Because most states now codify their criminal laws by enacting statutes, start there. Then look to any case law which may interpret these statutes. Since courts generally follow precedent due to the doctrine of stare decisis, one red flag that your behavior may be unlawful is that, in the past, the courts have found behavior similar to yours to be unlawful.
- Kerper, H. B. (1979). Introduction to the criminal justice system (2nd ed., pp. 27). West Publishing Company. ↵
- LaFave, W. R. (2000). Criminal law (3rd ed., pp. 70). St. Paul, Minn: West Group. ↵
- Vasquez v. Hillery, 474 U.S. 254 (1986) ↵
- Kerper, H. B. (1979). Introduction to the criminal justice system (2nd ed., pp. 47-49). West Publishing Company. ↵
- Kerper, H. B. (1979). Introduction to the criminal justice system (2nd ed., pp. 49). West Publishing Company. ↵