Pope Pius XI
Quadragesimo Anno §101
Quadragesimo Anno: On Reconstruction of the Social Order
101 With all his energy Leo XIII sought to adjust this economic system according to the norms of right order; hence, it is evident that this system is not to be condemned in itself. And surely it is not of its own nature vicious. But it does violate right order when capital hires workers, that is, the non-owning working class, with a view to and under such terms that it directs business and even the whole economic system according to its own will and advantage, scorning the human dignity of the workers, the social character of economic activity and social justice itself, and the common good.
Source: Quadragesimo Anno (Vatican.va)