Statutes are laws that have been written and passed by the legislative body within a jurisdiction. Although all efforts are made during the legislative process to create clear statutes, statutory law must still be interpreted by courts if a word, term, or phrase is vague or open to more than one interpretation. In civil law judicial systems, the courts have very little authority to interpret statutes; however, in common law legal systems, courts are often called upon to interpret or clarify statutory law. Courts use a variety of methods to do so, including the purpose and history of the legislation, as well as its conformity with other laws or agencies. Courts may also use canons of interpretation, which have been used since the time of the ancient Roman legal system.
When called on to interpret a statute, a judge will look to the purpose and history of the legislation. In most judicial systems, the process by which legislation is passed is a long and involved process. In most cases, there will be a written record that follows the legislation from start to finish, including debates over the legislation. A judge may use the information gained from the statute's history to help determine what the purpose of the legislation was, and apply that to the interpretation of any ambiguous terms.
When interpreting a statute, a judge will first attribute the common and accepted meaning to the words within the statute. A judge will also usually try to interpret statutory law in a way that it does not conflict with other laws or encroach upon another agency's jurisdiction. Of course, in some cases, there is no way to interpret the statute in a way that conforms with current legislation or that does not infringe upon another agency's jurisdiction.
A judge may also rely on ancient canons of construction when interpreting statutory law. Three basic categories of canons are used to interpret laws — deference, textual, and substantive. Within each category are a number of "canons," or general rules, that guide a judge in how to interpret a law. For example, one of the textual canons holds that when a list of items are specifically mentioned in a statute, then anything not on the list is not included unless the list is prefaced with a qualifier, such as "for example." Another example is the avoidance canon within the deference category, which calls for choosing the interpretation that does not create constitutional issues when a statute may be interpreted in more than one way.