The denomination with the longest history of objection to Freemasonry is the Roman Catholic Church. The objections raised by the Roman Catholic Church are based on the allegation that Masonry teaches a naturalistic deistic religion which is in conflict with Church doctrine. A number of Papal pronouncements have been issued against Freemasonry. The first was Pope Clement XII's In eminenti apostolatus, 28 April 1738; the most recent was Pope Leo XIII's Ab apostolici, 15 October 1890. The 1917 Code of Canon Law explicitly declared that joining Freemasonry entailed automatic excommunication, and banned books favouring Freemasonry.