This new work clarifies Aquinas concept of natural law through his biblical commentaries, and explores its applications to U.S. constitutional law. The first time the use of Aquinas on the U.S. Supreme Court has been explored in depth, and its applications tested through a rigorous reading of the biblical commentaries Shows how key judgments in the Supreme Court have rested on medieval natural law, and applies critical gender theory to discuss problems with these applications Offers new research data to give a different picture of Aquinas and natural law, and a fresh take on Aquinas biblical commentaries New research based on passages in the biblical commentaries never before available in English