18 February 1513,
The kings of Navarra were declared heretical by Pope July II. The excuse for excommunication was the alliance of Navarre with the kingdom of France enemy of the Vatican. This bull was signed by the Pope on 21 July 1512, when the Navarre invasion began. The king of Castile presses the pope to refer directly to the kings of Navarra.
Source:
Joseba Asiron and Martín Altzueta, 50 key dates of the conquest of Navarra (1512-1525). (Txalaparta)