Kammala jumla mai zuwa: A matsayin mai ba da fansa don wuce gona da iri na 1814, an kori Blacas ba bisa ƙa'ida ba a matsayin jakadan Faransa a kotun Masarautar Sicilies Biyu, wanda babban birninta yake a Naples. A can, ya yi shawarwari game da auren 1816 na dan uwan Louis XVIII, Duke na Berry, zuwa Francis I na Sicilies 'yar Caroline. Hakanan a cikin 1816, Blacas ya zama memba na duka Académie des Inscriptions et Belles-Lettres da kuma Académie des Beaux-Arts. Bayan haka, an nada shi jakadan Faransa a wurin Holy See a Rome. Ya sanya hannu kan yarjejeniya tsakanin Bourbon Faransa da Paparoma Pius VII a ranar 11 ga Yuni 1817. A cikin 1820, ya karɓi "Ordre du Saint-Esprit". Duk da yake har yanzu jakadan ne a Roma, ya kasance daya daga cikin wakilan Faransa uku a majalisar
Majalisa ta Laibach a shekara ta 1821.