Hume’s and Bentham’s criticisms of natural law theory are direct and even mocking. By contrast, Kant’s approach in the Feyerabend lectures is far more restrained. Having adopted for his course an author explicitly committed to natural law premises, Kant largely avoids open conflict with those premises, choosing instead to develop his claims about right without making any direct critique (or defense) of the appeal to natural law. What accounts for this difference? After briefly reviewing the history of natural law theory in the modern period, I turn to a close reading of Kant’s brief but pointed criticisms of Achenwall in the opening sections of the Feyerabend lectures. I argue that Kant understands a theory of natural law not as opposed to but as irrelevant to a theory of right. Once we appreciate this claim, we can better understand Kant’s equally important contribution to the decline of natural law theory in the tradition of liberal political theory.