I am curious. Is the prohibition on artificial birth control a dogmatic matter?
It is not to be thought that what is set down in Encyclical letters does not demand assent in itself, because in this the popes do not exercise the supreme power of their magisterium. For these matters are taught by the ordinary magisterium, regarding which the following is pertinent: “He who heareth you, heareth Me.” (Luke 10:16); and usually what is set forth and inculcated in Encyclical Letters, already pertains to Catholic doctrine. But if the Supreme Pontiffs in their acts, after due consideration, express an opinion on a hitherto controversial matter, it is clear to all that this matter, according to the mind and will of the same Pontiffs, cannot any longer be considered a question of free discussion among theologians.
—Humani Generis