49 Equal diligence and severity are to be used in examining and selecting candidates for Holy Orders. Far, far from the clergy be the love of novelty! God hates the proud and the obstinate. For the future the doctorate of theology and canon law must never be conferred on anybody who has not made the regular course of scholastic philosophy; if conferred it shall be held as null and void. The rules laid down in 1896 by the Sacred Congregation of Bishops and Regulars for the clerics, both secular and regular, of Italy concerning the frequenting of the Universities, We now decree to be extended to all nations. Clerics and priests inscribed in a Catholic Institute or University must not in the future follow in civil Universities those courses for which there are chairs in the Catholic Institutes to which they belong. If this has been permitted anywhere in the past, We ordain that it be not allowed for the future. Let the Bishops who form the Governing Board of such Catholic Institutes or Universities watch with all care that these Our commands be constantly observed.
Source: Pascendi Dominici Gregis (Vatican.va)