ex cathedra

With authority like that of the Pope. The expression, Latin words  meaning  “from  the  chair,”  literally  refers  to  the  doctrine  of  papal infallibility, whereby the Pope, in statements on faith and morals, cannot be wrong. It began to be used figuratively in the early nineteenth century. “He was  a  great  lover  of  form,  more  especially  when  he  could  dictate  it  ex cathedra” (Sir Walter Scott, Rob Roy, 1818).