This paper argues that Kant’s ethics and Kant’s philosophy of right are linked by a common normative idea. I try to show that we find in Kant’s exposition of the basic normative principles in the Groundwork the resources for grounding his philosophy of right. More specifically, my point is that Kant’s conception of a realm of ends, as he develops it in the Groundwork, provides a common normative source for Kant’s ethical Categorical Imperatives, on the one hand, and the Universal Principle of Right, on the other. The agreement on common universal principles, as it is crucial for Kant’s notion of a realm of ends, yields, so my claim, a justification of the ethical Categorical Imperatives and the Universal Principle of Right. I develop this agreement-based justification in the form of a transcendental argument, thus aiming to show that it squares with Kant’s methodologicalapproach in the Groundwork.