In fact, this amounts to a prohibition to fulfill the commandment of Christ. “Go and preach”, “go and teach all nations”, “and they went and preached”, says the Gospel about Christ’s direct command to his apostles.
The sermon can only be prohibited by the hierarchy, which in fact is the metropolitan. And the reason for the ban can be serious canonical violations: the preacher speaks of heresy, or some incredible crimes have been noticed behind him. If the flock accepts its pastor and his words, and the hierarchy does not forbid him to speak, the interference of the secular authorities in the affairs of the Church is illegal. Only the extremely godless Soviet government, which directly persecuted the church, decided on such a thing, and even then with digressions and reservations.
