But today, Pickett said, natural law theory is mostly used to justify differential treatment of LGBTQ people. In a 2004 critique, Pickett explained that, since the natural law view of sexuality holds that “sex must be related to a human ‘good’—in this case, the possibility of procreation—in order to be just,” its proponents commonly defend anti-LGBTQ policies from anti-sodomy laws to legal discrimination as grounded in human reason, rather than faith. The same rationales, he adds, are used to argue against contraception.

As a legal strategy, it’s a better bet than citing scripture. “It’s a way to achieve the same goals of religious conservatives without making clear that that’s what’s going on,” said Peter Montgomery, a senior fellow at People for the American Way.