9 According to these rules, Venerable Brethren, you should judge those to whom you will entrust the ministry of the divine word. Whenever you find any of them departing from these rules, being more concerned with their own interests than those of Jesus Christ and more anxious for worldly applause than the welfare of souls, warn and correct them. If that proves insufficient, be firm in removing them from an office for which they have proven themselves unworthy. You should be especially diligent in employing this vigilance and severity since the ministry of preaching belongs in a special way to you, and is one of the chief functions of the Episcopal Office. Whoever outside your rank preaches, he does so only in your name and in your place. It follows, therefore, that you are always responsible before God for the way in which the bread of the divine word is distributed to the faithful. In order to remove all responsibility from Our shoulders, We notice and command all Ordinaries to discontinue or suspend, after charitable warnings, any preacher, be he secular or regular, and even if it be during a course of sermons, who does not completely obey the regulations laid down in the above-mentioned Instruction of the Congregation of Bishops and Regulars. Better by far would it be if the faithful were satisfied with the simple homilies and explanations of the Catechism their parish priests offer them than to attend sermons that do more harm than good.
Source: Pieni L'Animo (Vatican.va)