If we accept the definition of obsolete rites as those ”out of harmony with prevailing laws and rubrics,” then the answer is quite simple if one is a papal positivist. Pius XII writes, ”the Sovereign Pontiff alone enjoys the right to recognize and establish any practice touching the worship of God, to introduce and approve new rites, as also to modify those he judges to require modification” (58 ). The pope can change the ”prevailing laws and rubrics” so that those obsolete rites are no longer ”out of harmony with prevailing laws and rubrics.”