CHAPTER VII
ON THE INTERPRETATION OF LAW
I. THE interpretation of law is its genuine explanation according to the mind of the lawgiver.
(a) This interpretation may be authentic, doctrinal, or customary.
Laws are authentically interpreted by the lawgiver, his successor, and by him to whom this power of interpreting the law has been granted by them.
An authentic interpretation set forth by way of law has the same force as the law itself; and if it only declares the words of the law which in themselves are certain, it does not need to be promulgated and it has a retrospective force; if it restricts or extends the law or if it explains a doubtful law, it has not a retrospective force and it should be promulgated. But if it is given by way of judicial sentence or rescript in a particular matter, it has not the force of law, and it only binds the persons and affects the matters for which it was given (Can. 17).
Doctrinal interpretation is that which doctors and lawyers make according to the recognized rules of legal interpretation. It has weight according to the knowledge, skill, experience, and standing of him who makes the interpretation.
Customary interpretation is that which a law receives from the practice and conduct of those who are subject to it. It has very great authority, for it is presumed to have at least the tacit approval of the lawgiver, and indeed, according to the adage, " Custom is the best interpreter of law " (Can. 29).
(b) A strict interpretation takes the words of the law in their literal meaning; a wide interpretation takes the words in a looser sense.
2. Many rules are given by canonists for the doctrinal interpretation of law. The following are the most important for our purpose in moral theology:
(a) The words of the law must be taken in their obvious and natural meaning. The lawgiver must be supposed to have wished to express himself as clearly as possible, and to have said what he meant. Sometimes, however, legal terms have a technical meaning which must be attended to. Thus,
