Sterilization

It would be more than a mere lack of readiness in the service of life if an attack made by man were to concern not only a single act but should affect the organism itself to deprive it, by means of sterilization, of the faculty of procreating a new life. Here, too, you have a clear rule in the Church's teaching to guide your behavior both interiorly and exteriorly. Direct sterilization— that is, whose aim tends as a means or as an end at making procreation impossible—is a grave violation of the moral law and therefore unlawful. Not even public authority has any right, under the pretext of any "indication" whatsoever, to permit it, and less still to prescribe it or to have it used to the detriment of innocent human beings.

This principle is already proclaimed in the above mentioned Encyclical of Pius XI on marriage. Thus when ten years or so ago sterilization came to be more widely applied, the Holy See saw the necessity of expressly and publicly declaring that direct sterilization, either perpetual or temporary, in either the male or the female, is unlawful according to natural law, from which, as you well know, not even the Church has the power to dispense.

As far as you can, oppose, in your apostolate, these perverse tendencies and do not give them your cooperation.