Pie XI

If the Roman Church is to find any way out of the crisis into which nationalism has brought it, then it must be thoroughly transformed. It may be that this transformation and reformation will lead to its unconditional acceptance of the indispensability of private ownership in the means of production. At present it is still far from this, as witness the recent encyclical Quadragesimo anno.

Mises, Socialism, pp. 386f

http://w2.vatican.va/content/pius-xi/en/encyclicals/documents/hf_p-xi_enc_19310515_quadragesimo-anno.html

Principe de subsidiarité

As history abundantly proves, it is true that on account of changed conditions many things which were done by small associations in former times cannot be done now save by large associations. Still, that most weighty principle, which cannot be set aside or changed, remains fixed and unshaken in social philosophy: Just as it is gravely wrong to take from individuals what they can accomplish by their own initiative and industry and give it to the community, so also it is an injustice and at the same time a grave evil and disturbance of right order to assign to a greater and higher association what lesser and subordinate organizations can do.

Pie XI http://w2.vatican.va/content/pius-xi/en/encyclicals/documents/hf_p-xi_enc_19310515_quadragesimo-anno.html