"Men, in a church or outside a church, while they are assisting at sacred rites, shall be bare-headed, unless the approved mores of the people or peculiar circumstances of things determine otherwise; women, however, shall have a covered head and be modestly dressed, especially when they approach the table of the Lord."

Canon 22 (1983 Code of Canon Law #20) says:

"A later law, laid down by the competent authority, [abrogates] a prior law if it expressly says so, or if it is directly contrary to it, or if it completely reorders the matter treated in the earlier law; but, and though observing Canon 6, n.1, general laws in no way derogate from the special [laws] of places and from the statutes of [inferior authorities], unless expressly established otherwise in the law."

Canon 27 number 1 (1983 Canon 26 n.1):
"No custom can derogate from divine law, whether natural or positive; neither can it prejudice ecclesiastical law, unless the custom was reasonable and has been observed for forty continuous and complete years; but against an ecclesiastical law that contains a clause prohibiting future customs, only a reasonable custom can be prescriptive if it is centenary or immemorial."

Canon 27 number 2 (1983 Canon 26 n.2):
"A custom that is expressly reprobated in law is not reasonable."