11 One can readily understand that it was not easy for Us to pass judgment on this question. In the first place, We could not and We did not even wish it to be made to appear that We were willing to accept a different solution from that which had been outlined by Pius X. Both the memory and the position taken by the great Pontiff who was Our Predecessor made such a course impossible; the violation of the rights of this Apostolic See and of the hierarchy, rights which are the rights of God and of souls, simply forbade such a course. What We did do was to ask for the prayers of many of the faithful, and We too lifted Our heart to God in prayer, and then after considering at great length the matter in the Divine Presence, We confirmed the condemnation which had been made of the iniquitous law of separation, but at the same time concluded that, due to the change in public opinion, and, due also to the different circumstances and relations between the Holy See and the French Republic which had toward the end of 1922 been so profoundly changed, We did not see any difficulty which would keep Us from allowing the Diocesan Associations to come into existence, at least as an experiment, but only on the following condition. First, the statutes would have to be corrected in such a way that they would conform, both in their general tenor and in their essential nature, with the divine constitution and laws of the Church. Secondly, We must be given certain guaranties, protected by law, which would remove as far as possible all danger that in case men hostile to the Church should come into power in the Republic, they might be able to refuse to recognize the legal existence and the legal rights of these Associations, and thus expose them to the possibility of losing their property which they held under the law.
Source: Maximam Gravissimamque (Vatican.va)