As pope he became an active and vigorous reformer of the Church. He reasserted control over the Papal States and was acknowledged as the overlord of Sicily. In Germany he asserted the pope’s right to choose between two rival candidates for the imperial crown; he eventually supported Frederick II’s claims provided that he did homage for Sicily. He intervened in English affairs, excommunicating King John for refusing to recognize Stephen Langton as Archbishop of Canterbury and declaring Magna Carta void; he also attempted to curb the independence of Philip II of France.