Several commentators have tried to ground legal prohibitions of kidney sales in some form of Kant’s moral arguments against such sales. This paper reconsiders this approach to justifying laws and policies in light of Kant’s approach to law in his political philosophy. The author argues that Kant’s political philosophy requires that kidney sales be legally permitted, although contracts for such sales must remain unenforceable. The author further argues that Kant’s approach to laws, such as those governing kidney distribution, was formed in part by considering and rejecting an assumption frequently employed in the bioethics literature, namely, that legal duties can be grounded directly in moral duties. The author explains some of Kant’s reasons for rejecting this assumption and concludes that arguments pertaining to the legality of kidney sales developed on the basis of Kant’s moral philosophy should no longer be considered tenable.