Statutory law is law that is made by a legislature and codified or written down in code books. It is primarily a concept that exists in common law systems in order to underscore the distinction between laws that a governing body makes and case law. Many countries are common law systems, including the United States, Scotland, Canada, Israel, and Nicaragua.
In the United States and other common law systems, law is made by legal cases. This means that when a judge decides a case, his decision or rule essentially becomes the law that governs all similar cases. Judges make these laws, so a common law system is also called a case law system.
While judges can and do make case law in a common law system, the legislature or executive branch also makes law. In the United States, the Constitution clearly sets forth this distinction in the Constitution under the doctrine of "Separation of Powers." The Constitution reserves the right for the legislative branch of the federal government to make laws regulating certain issues, and state constitutions do the same in many states.
If the legislature, whether at the state or federal level, makes a law, that law is statutory law. A statutory law is often published as a bill in the United States and Canada, while other common law countries may have their own names for statutory laws that are published. Normally when a bill is passed, it becomes law right away, and is eventually codified or written down in formal code books that contain lists of statutes.
This statutory law governs in conjunction with case law. The statute is the fundamental law that must be followed. Statutes, however, do not always govern every single possible situation and are often open to interpretation.
If a statute is open to being interpreted, the courts can interpret it according to set principles. Generally, the rules dictate that if the plain language of a statute says something, whatever it says is the law. If the plain language leaves room for ambiguity, either the court or a state agency vested with the power to interpret the statute can make an interpretation.
When courts or state agencies interpret statutory law, they must follow basic rules of interpretation to ensure that the intent of the statute is followed. This means the courts or agencies must look to legislative history to interpret the statute. Once the courts or agencies interpret the statute, their interpretation becomes the law, unless or until the legislature passes a new law amending the interpretation.