Principe de subsidiarité

However, the right of self-determination of which we speak is not the right of self-determination of nations, but rather the right of self-determination of the inhabitants of every territory large enough to form an independent administrative unit. If it were in any way possible to grant this right of self-determination to every individual person, it would have to be done. This is impracticable only because of compelling technical considerations, which make it necessary that a region be governed as a single administrative unit and that the right of self-determination be restricted to the will of the majority of the inhabitants of areas large enough to count as territorial units in the administration of the country.

Ludwig von Mises, Liberalism, ch. 3 [1]

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