A false prophet is to be judged only by the court of 71. How we do know that? The Gemara uses verses with the same term to derive it -- and then revises which term is the one to learn the halakhah from, both as linked to the case of the rebellious elder (zaken mamre). Also, extending the city limits of Jerusalem, only with the court of 71. With a side discussion (that takes over) into the vessels of the Temple.