ex ca·the·dra 
(ĕks′ kə-thēdrə)
(ĕks′ kə-thēdrə)adv. & adj.
With the authority derived from one's office or position: the pope speaking ex cathedra; ex cathedra determinations.
[Latin ex cathedrā : ex, from + cathedrā, ablative of cathedra, chair.]