Natural law theory in the Aristotelian-Thomistic (A-T) tradition is grounded in a metaphysics of essentialism and teleology, and in turn grounds a theory of natural rights. This chapter offers a brief exposition of the metaphysical ideas in question, explains how the A-T tradition takes a natural law moral system to follow from them, and also explains how in turn the existence of certain basic natural rights follows from natural law. It then explains how the teleological foundations of natural law entail not only that natural rights exist, but also that they are limited or qualified in certain crucial ways. The right to free speech is used as a case study to illustrate these points. Finally, the chapter explains the sense in which the natural rights doctrine generated by A-T natural law theory amounts to a theory of human rights, specifically.