Pope Leo X.
Bulla super impressione librorum.
On May 3, 1515, during the Fifth Lateran Council, Pope Leo X issued the Bulla super impressione librorum, the first universally accepted papal censorial decree. All writings without exception were subjected to ecclesiastical censorship, and the examination was entrusted to the bishops or censors appointed by them and to the inquisitor. Printers disobeying the decree could be excommunicated and fined, and their books burnt. Leo’s successors issued much more stringent papal decrees on censorship, culminating in the first index of prohibited books in 1559.