Natural law does not depend upon religious orthodoxy, though it is often associated with it. One can defend natural rights from the perspective of being inherent in our existence as rational beings rather than Sky-King's (Sky-Kingses' for the polytheistic?) decree.

Further, large numbers of people with at least some theistic leanings were/are nevertheless adherents to legal positivism, which explains how you can have Catholics or Lutherans that were okay with the Nuremberg Laws, for example.

> One can defend natural rights from the perspective of being inherent in our existence as rational beings rather than Sky-King's (Sky-Kingses' for the polytheistic?) decree.

That’s just creating a religion, complete with supernatural assertions—things that are “inherent our existence” but can’t be established empirically—without copping to it.

I dare you to make this same argument in the context of the 2nd Amendment and see how well it goes down with your conservative friends.

The mainstream conservative argument for the second amendment would be that it reflects our history and tradition; our forefathers adopted the second amendment based on their experience building a free society and it’s the law of the land until the proper procedures are followed to change it. But I don’t think I’d rile up any conservatives if I pointed out that say Japan has a different history and tradition, and that it’s not a violation of any “universal human rights” for them to restrict firearms ownership. They might assert that our way is better than the Japanese way, but few would deny that the Japanese have the right and the prerogative to restrict firearms ownership if that’s what they choose to do.

That is not to say that conservatives don’t believe in “universal human rights”—for example those who believe that a society can’t permit abortion because it violates the right to life. But conservatives don’t deny that they believe in a God we can’t see that makes rules for the world.

“Universal human rights” tends to reflect in practice the individualistic quasi-religious beliefs of European-descended liberals. In an international context it functions as a form of cultural supremacy by people who claim to reject such ideas. But isn’t it curious how on everything from the nature of marriage, to familial obligation, to sexual morality, to criminal justice, to when it’s okay to extinguish nascent human life, societies run by white people have figured out the correct “universal” answer while Bangladeshis, Nigerians, and apparently even Singaporeans have got it all wrong? This is a harder road to hoe for people who claim not to believe that their society is chosen by God to be a shining city on a hill.