What's the noun for magisterial? Here's the word you're looking for.
magistrate
(law) A judicialofficer with limited authority to administer and enforce the law. A magistrate's court may have jurisdiction in civil or criminal cases, or both.
(historical) A high official of the state or a municipality in ancient Greece or Rome.
(historical, by extension) A comparable official in medieval or modern institutions.
“He answered, 'Their writings are only to be understood by the adepts, without whom no student can prepare this magistery.”
“The jurists, who multiply commentaries, model themselves after the theologians by practicing the Spagyric Magistery.”
“This year's winners include Stegall, John Jacob Magistery, and Nightmare Air.”
magister
Master; sir: a title used in the Middle Ages, given to a person in authority, or to one having a license from a university to teach philosophy and the liberal arts.
“Amicitia principum, friendship with the emperor, was a sure way of gaining access to senatorial magistracies and other honorable positions.”
“Other magistracies, the aedileship and the tribunate of the plebs, might be held between quaestorship and praetorship, but were not obligatory.”
“Apart from the traditional magistracies, his only posts were those of imperial legate in Italy, in his case in Etruria and Umbria, where he owned land, and proconsul of Asia.”