It's easy for religious leaders to create new laws, but it's harder to convince believers to follow them.

At least, that's what the Benediction monk Gratian -- a canon law pioneer -- argued in the 12th century: "Laws are established when they are promulgated. … They are confirmed when they have been approved by the long term and reasoned acceptance of those who observe them."

Anyone doubting this wisdom should study Catholic social media, noted Cardinal Walter Brandmuller, the 92-year-old former leader of the Pontifical Committee for Historical Sciences. There has been a "hurricane" in the "blogger scene and other media" in response to Traditionis Custodes ("Guardians of the tradition"), the effort by Pope Francis to bind those who celebrate the traditional Latin Mass.

When confusion surrounds a new "ecclesiastical law" -- as opposed to scripture and "natural law" doctrines -- it's important to remember that its "validity … ultimately depends on the consent of those affected by it," wrote Brandmuller, at Kath.net in Germany.

"The law must serve the good of the community, and not vice versa. … If a law is not observed, or is no longer observed, whether from the beginning or after a time, it loses its binding force and becomes obsolete."

The pope's declaration has unleased waves of grief among supporters of the now retired Pope Benedict XVI and his apostolic letter Summorum Pontificum ("Of the Supreme Pontiffs"), which claimed the post-Vatican II Novus Ordo was the "ordinary form" for the modern Mass, but that the older Tridentine rite was an "extraordinary form" that could be encouraged.

This fight is "not really about rites at all, wrote Father Raymond J. de Souza, at First Things. It's about Catholic life in the age of the Internet. The Mass is the message."

The question is how Pope Francis will apply his ruling that the modern Mass is now the "unique expression" of the Catholic "lex orandi" (the law of what is prayed). Will this affect Byzantine liturgies used by Eastern Rite Catholics or rites approved for former Anglicans?