St Thomas Aquinas
teaches that those who throw contempt on the customs of the Church ought to be "punished as those who disobey the law of God"
...and yet we see how the liturgical laws and traditions of the Church have been radically altered and many now throw contempt on such traditions
"On change in laws"
Article 2. "Whether human law should always be changed, whenever something better occurs?"
Objection 1. It would seem that human law should be changed, whenever something better occurs. Because human laws are devised by human reason, like other arts. But in the other arts, the tenets of former times give place to others, if something better occurs. Therefore the same should apply to human laws.
Objection 2. Further, by taking note of the past we can provide for the future. Now unless human laws had been changed when it was found possible to improve them, considerable inconvenience would have ensued; because the laws of old were crude in many points. Therefore it seems that laws should be changed, whenever anything better occurs to be enacted.
Objection 3. Further, human laws are enacted about single acts of man. But we cannot acquire perfect knowledge in singular matters, except by experience, which "requires time," as stated in Ethic. ii. Therefore it seems that as time goes on it is possible for something better to occur for legislation.
On the contrary, It is stated in the Decretals (Dist. xii, 5): "It is absurd, and a detestable shame, that we should suffer those traditions to be changed which we have received from the fathers of old."
I answer that, As stated above (Article 1), human law is rightly changed, in so far as such change is conducive to the common weal. But, to a certain extent, the mere change of law is of itself prejudicial to the common good: because custom avails much for the observance of laws, seeing that what is done contrary to general custom, even in slight matters, is looked upon as grave. Consequently, when a law is changed, the binding power of the law is diminished, in so far as custom is abolished. Wherefore human law should never be changed, unless, in some way or other, the common weal be compensated according to the extent of the harm done in this respect. Such compensation may arise either from some very great and every evident benefit conferred by the new enactment; or from the extreme urgency of the case, due to the fact that either the existing law is clearly unjust, or its observance extremely harmful. Wherefore the jurist says [Pandect. Justin. lib. i, ff., tit. 4, "De Constit. Princip."] that "in establishing new laws, there should be evidence of the benefit to be derived, before departing from a law which has long been considered just."
Reply to Objection 1. Rules of art derive their force from reason alone: and therefore whenever something better occurs, the rule followed hitherto should be changed. But "laws derive very great force from custom," as the Philosopher states (Polit. ii, 5): consequently they should not be quickly changed.
Reply to Objection 2. This argument proves that laws ought to be changed: not in view of any improvement, but for the sake of a great benefit or in a case of great urgency, as stated above. This answer applies also to the Third Objection.
Article 3. "Whether custom can obtain force of law?"
Objection 1. It would seem that custom cannot obtain force of law, nor abolish a law. Because human law is derived from the natural law and from the Divine law, as stated above (93, 3; 95, 2). But human custom cannot change either the law of nature or the Divine law. Therefore neither can it change human law.
Objection 2. Further, many evils cannot make one good. But he who first acted against the law, did evil. Therefore by multiplying such acts, nothing good is the result. Now a law is something good; since it is a rule of human acts. Therefore law is not abolished by custom, so that the mere custom should obtain force of law.
Objection 3. Further, the framing of laws belongs to those public men whose business it is to govern the community; wherefore private individuals cannot make laws. But custom grows by the acts of private individuals. Therefore custom cannot obtain force of law, so as to abolish the law.
On the contrary, Augustine says (Ep. ad Casulan. xxxvi): "The customs of God's people and the institutions of our ancestors are to be considered as laws. And those who throw contempt on the customs of the Church ought to be punished as those who disobey the law of God."
I answer that, All law proceeds from the reason and will of the lawgiver; the Divine and natural laws from the reasonable will of God; the human law from the will of man, regulated by reason. Now just as human reason and will, in practical matters, may be made manifest by speech, so may they be made known by deeds: since seemingly a man chooses as good that which he carries into execution. But it is evident that by human speech, law can be both changed and expounded, in so far as it manifests the interior movement and thought of human reason. Wherefore by actions also, especially if they be repeated, so as to make a custom, law can be changed and expounded; and also something can be established which obtains force of law, in so far as by repeated external actions, the inward movement of the will, and concepts of reason are most effectually declared; for when a thing is done again and again, it seems to proceed from a deliberate judgment of reason. Accordingly, custom has the force of a law, abolishes law, and is the interpreter of law.
Reply to Objection 1. The natural and Divine laws proceed from the Divine will, as stated above. Wherefore they cannot be changed by a custom proceeding from the will of man, but only by Divine authority. Hence it is that no custom can prevail over the Divine or natural laws: for Isidore says (Synon. ii, 16): "Let custom yield to authority: evil customs should be eradicated by law and reason."
Reply to Objection 2. As stated above (Question 96, Article 6), human laws fail in some cases: wherefore it is possible sometimes to act beside the law; namely, in a case where the law fails; yet the act will not be evil. And when such cases are multiplied, by reason of some change in man, then custom shows that the law is no longer useful: just as it might be declared by the verbal promulgation of a law to the contrary. If, however, the same reason remains, for which the law was useful hitherto, then it is not the custom that prevails against the law, but the law that overcomes the custom: unless perhaps the sole reason for the law seeming useless, be that it is not "possible according to the custom of the country" [95, 3], which has been stated to be one of the conditions of law. For it is not easy to set aside the custom of a whole people.
Reply to Objection 3. The people among whom a custom is introduced may be of two conditions. For if they are free, and able to make their own laws, the consent of the whole people expressed by a custom counts far more in favour of a particular observance, that does the authority of the sovereign, who has not the power to frame laws, except as representing the people. Wherefore although each individual cannot make laws, yet the whole people can. If however the people have not the free power to make their own laws, or to abolish a law made by a higher authority; nevertheless with such a people a prevailing custom obtains force of law, in so far as it is tolerated by those to whom it belongs to make laws for that people: because by the very fact that they tolerate it they seem to approve of that which is introduced by custom.