You seem to be stating a pre-Vatican concept that fails to understand that 'nature' has many meanings and much ambiguity.  In the old concept, natural law referred to the eternal plan of God, discovered by reason and true for all times, places, and circumstances.  It was universal, unchangeable.  It wanted moral certitude.  


As a church, a new age was entered after Vatican II, which gives more importance to the particular, the contingent, the historical, and the changing.  Each culture has a history, with different contingent historical situations.  We are living on one planet and ultimately are connected with other people living on our world.  Yet, we also have to be open to diversity, particularity, and individuality. 
 

We can no longer accept that 'THE TRUTH', is something that objectively exists "out there," apart from history, and expressed in unchangeable propositions.  The subjective human consciousness must also be taken into account---in our post-modern world.