45 Let the working man and the employer make free agreements, and in particular let them agree freely as to the wages; nevertheless, there underlies a dictate of natural justice more imperious and ancient than any bargain between man and man, namely, that wages ought not to be insufficient to support a frugal and well-behaved wage-earner. If through necessity or fear of a worse evil the workman accept harder conditions because an employer or contractor will afford him no better, he is made the victim of force and injustice. In these and similar questions, however - such as, for example, the hours of labor in different trades, the sanitary precautions to be observed in factories and workshops, etc. - in order to supersede undue interference on the part of the State, especially as circumstances, times, and localities differ so widely, it is advisable that recourse be had to societies or boards such as We shall mention presently, or to some other mode of safeguarding the interests of the wage-earners; the State being appealed to, should circumstances require, for its sanction and protection.
Source: Rerum Novarum (Vatican.va)