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.
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THIRD ARTICLE [I-II, Q. 97, Art. 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 (Q. 93, A. 3; Q. 95, A. 2).
But human custom cannot change either the law of nature or the Divine
law. Therefore neither can it change human law.

Obj. 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.

Obj. 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, abolishe