A Bull of Pius IX makes some modification in these regulations. The excommunication (reserved as papal) comes into effect through the reading of works which are written by heretics or apostates, or which present or defend heresy. But this would not exclude weekly or daily periodicals which might in some of their columns contain pernicious matter. Books produced by writers outside of the Church are held as less pernicious than the works of Catholics who have become Free-Thinkers, Rationalists, or Spiritualists, and who are, therefore, to be classed as apostates.[87] From the middle of the 16th century, there are instances of public protest and of action on the part of political rulers against the promulgation of the _Bulla Coenae_ or the enforcement of its penalties. In 1536, a commentary by the jurist Pierre Reboeuf on the Bull was confiscated in Paris. In 1551, Charles V prohibits the printing of the Bull in Spain. In 1568 Philip II confirms this prohibition, and asks the pope to recall the Bull as far as Spain was concerned. In 1570, the publication of the Bull is forbidden in Naples. In 1568, the Senate of Venice forbids the publication; but in 1570 the Council of Ten permits the reading of the Bull in the churches on Maundy Thursday. In 1582, Philip II prohibits the publication in Portugal. In 1580, Henry III prohibits the publication in France. In 1586, Rudolph II prohibits the publication in Bohemia, Moravia, and Silesia. _1524._ _Adrian VI_ adds “and Martin Luther, and all who read, listen to, distribute, or possess his writings, or defend the teachings in the same.” _1536._ _Paul III_, in a reissue of the _Bulla Coenae Domini_, adds the words: “We excommunicate and anathematise ... all heretics, the Kathareni, the Patareni ... who are followers of the godless and abominable heresies of Martin Luther, condemned by Leo X, and all who favour or protect him in any way, and all who read or distribute the writings of said Martin.” _1583._ _Gregory XIII_, in a Bull issued April 4th, modifies this _Passus_ to the form which is followed in the later Bulls: “We excommunicate ... all Hussites, Wyclifites, Lutherans, Zwinglians, Calvinists, Huguenots, Anabaptists, (anti)-Trinitarians, and all heretics of whatever name or sect, and their followers (_eorum credentes_) and protectors, and all those who print, distribute, possess, or read the writings of these heretics, or any books which attempt to undermine the authority of the Apostolic Chair,” etc. Since Julius II (1503) it is ordered[88] in the Bull that it shall be formally promulgated by all bishops once each year. Gregory XIII directs all pastors and confessors to keep copies for diligent study. The day selected is usually the Thursday before Easter (Maundy Thursday).