What Thomas considered law and the American Constitution considers the basis of law are two different things.  Saint John Paul would be correct if he took the papacy out of the equation of the formation of natural law.  It has corrupted reason in its current form because it brooks no dissent.  Natural law reason must be marked by free inquiry or it is just authority.  Binding and loosening was not bound by Christ and it is why the Church can make radical changes in doctrine that may leave your head spinning but will restore balance when teaching has gone down a blind alley.  By the way, I have great faith.  I believe that the Church will right itself instead of sinking.  Many have just given up on her.