It is to CATHOLICS!!!
As long as someone in AUTHORITY has made the claim; who are they; a mere pew warmer; to challenge it?
"If he will not listen to the church, treat him as a pagan or tax collector." -Jesus
Why do Protestants accept Luther's authority to promulgate novel doctrines, like Sola Scriptura, when there is no evidence for it in the Bible, the early Church, or the first 1500 years of Christian history?