Can. 24 §1 No custom which is contrary to divine law can acquire the force of law.

§2 A custom which is contrary to or apart from canon law, cannot acquire the force of law unless it is reasonable; a custom which is expressly reprobated in the law is not reasonable.

Can. 25 No custom acquires the force of law unless it has been observed, with the intention of introducing a law, by a community capable at least of receiving a law.

Can. 26 Unless it has been specifically approved by the competent legislator, a custom which is contrary to the canon law currently in force, or is apart from the canon law, acquires the force of law only when it has been lawfully observed for a period of thirty continuous and complete years. Only a centennial or immemorial custom can prevail over a canonical law which carries a clause forbidding future customs.

Can. 27 Custom is the best interpreter of laws.

Can. 28 Without prejudice to the provisions of can. 5, a custom, whether contrary to or apart from the law, is revoked by a contrary custom or law. But unless the law makes express mention of them, it does not revoke centennial or immemorial customs, nor does a universal law revoke particular customs.