Digger,
You’ve provided your own answer. When you say “…general liturgical principles that prohibit anyone except the appropriate authority from changing this or that liturgical law.”
And again, we must keep in mind that the canonical use of the word “custom” does not mean the same thing it means in our everyday vocabulary. “Custom” does not merely mean “we feel like doing it this way” Too many people think that’s what the word means. It doesn’t.
If you’d like a specific law prohibiting future customs, here it is:
- Regulation of the Sacred Liturgy depends solely on the authority of the Church, that is, on the Apostolic See and, as laws may determine, on the bishop.
- In virtue of power conceded by the law, the regulation of the Liturgy within certain defined limits belongs also to various kinds of competent territorial bodies of bishops legitimately established.
- Therefore no other person, even if he be a priest, may add, remove, or change anything in the Liturgy on his own authority.
Sacrosanctum Concilium Second Vatican Council - Constitution on the Sacred Liturgy - Promulgated by Pope Paul VI (December 4, 1963)
That’s a pretty clear statement prohibiting future (from the perspective of 1963) changes.