The Roman Catholic Church has been among the most persistent critics of Freemasonry. The Church has prohibited its members from being Freemasons since "In eminenti apostolatus" in 1738. Since then, the Vatican has issued several papal bulls banning membership of Catholics from Freemasonry under threat of excommunication. In 1983, the Canon Law was changed to read: "A person who joins an association which plots against the Church is to be punished with a just penalty; however, a person who promotes or directs an association of this kind is to be punished with an interdict", thus eliminating the penalty of excommunication for Masons. Joseph Ratzinger, who later became Pope Benedict XVI, wrote in a letter that those who enroll in Masonic associations are in a state of grave sin and may not receive Holy Communion; the penalty of excommunication is not declared in the current code of canon law, but membership remains forbidden. However, the letter does not form part of Canon Law and during his tenure Benedict XVI did not make any attempt to change Canon Law to explicitly mention the ban on Freemasonry.