Natural Flaw?

I have been noticing an uptick in Protestants employing Natural Law as a basis for arguing for one set of moral/political/social imperatives or another. For the most part I have associated Roman Catholicism with Christian natural law, nonetheless, it’s gaining wider currency. What concerns me about this is that, outside narrow legal or academic discourses, the term “natural law” is incredibly open to abuse. This is somewhat analogous to how the word “theory” is deployed in science versus and in the popular imagination.

What is natural? This is a difficult question for Christians since Christianity suggests that the world is broken. What is the evidence that something is natural? That is occurs in nature? All kinds of animals engage in behaviours that would seem unequivocally gay, but then Al Mohler suggests that this is because our world is fallen. So an appeal to natural law folds back into an appeal to divine command in this scenario, and indeed it would seem the same way in most Christian applications of natural law. The Christian can argue for a particular moral behaviour on the basis of natural law, but if that precept is challenged then it’s back to the Bible. So long as what is “natural” is congruous with the Bible, then it’s all about natural law, where it deviates then this is just about the fall. It’s akin to me saying that every day will have pleasant weather but on the days that there is foul weather I’m still correct because our fallen world sometimes has bad weather. Whether or not this is true, you still wouldn’t hire me to tell you about the weather.

So does the category of natural law mean anything at all in Christian apologetics or Christian ethics? Or is it all just a front for divine command-type arguments? (Not that there’s anything wrong with arguing from divine command – especially for the believer – it’s just disingenuous to start by saying “this is grounded in nature” and then shifting gears if one is shown wrong.) A lot of what we might think of as natural law may be more likened to tradition or custom and it’s not at all clear to me why these arguments along with the aforementioned divine command business insufficient for natural law fans.