 From 1957 to 1971, he served as Librarian and Archivist of the Holy Roman Church.Under Pius XII, Tisserant also headed a commission to investigate alleged abuses of appointments in the Order of Malta, which concluded that there was no wrongdoing.In 1939, Tisserant urged Pius XII to promulgate an encyclical "on the duty of Catholics to resist the unjust orders of an authoritarian state."