#3 depending on how we define our terms. I disdain the term "natural law"...There's nothing 'natural' about it. If we are voting #3 because of Romans 1 then we have to cry uncle and say that it is the law of God written on men's hearts. No God = No Law. But that is exactly the purpose of using natural law. I don't have a problem arguing from a natural law perspective just would rather push the necessity of God from an ethical transendental perspective and get on with using Scripture.
