Noscitur a sociis

Statutory interpretation is the process by which courts interpret and apply legislation. Some amount of interpretation is often necessary when a case involves a statute. Sometimes the words of a statute have a plain and straightforward meaning. But in many cases, there is some ambiguity or vagueness in the words of the statute that must be resolved by the judge. To find the meanings of statutes, judges use various tools and methods of statutory interpretation, including traditional canons of statutory interpretation, legislative history, and purpose. In common law jurisdictions, the judiciary may apply rules of statutory interpretation both to legislation enacted by the legislature and to delegated legislation such as administrative agency regulations.

Statutory interpretation first became significant in common law systems, of which England is the exemplar. In Roman and Civil law, a statute (or code) guides the magistrate, but there is no judicial precedent. In England, Parliament historically failed to enact a comprehensive code of legislation, which is why it was left to the courts to develop the common law; and having decided a case and given reasons for the decision, the decision would become binding on later courts.

Accordingly, a particular interpretation of a statute would also become binding, and it became necessary to introduce a consistent framework for statutory interpretation. In the construction (interpretation) of statutes, the principle aim of the court must be to carry out the "Intention of Parliament", and the English courts developed three main rules (plus some minor ones) to assist them in the task. These were: the mischief rule, the literal rule, and the golden rule.

Statutes may be presumed to incorporate certain components, as Parliament is "presumed" to have intended their inclusion. For example:

Where legislation and case law are in conflict, there is a presumption that legislation takes precedence insofar as there is any inconsistency. In the United Kingdom this principle is known as parliamentary sovereignty; but while Parliament has exclusive jurisdiction to legislate, the courts (mindful of their historic role of having developed the entire system of common law) retain sole jurisdiction to interpret statutes.

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