The United Nations promoted a novel idea in the 1990s: National Human Rights Institutions (NHRIs). Their codification in the Paris Principles and subsequent UN General Assembly endorsement precipitated a global norm cascade. We demonstrate that NHRIs have spread rapidly. Furthermore, we document that structures established after UN endorsement have just as many institutional safeguards as earlier NHRIs. What explains this compliance pull? A transgovernmental NHRI network operating a system of independent monitoring of NHRIs is an important part of the explanation. We examine how this network has interacted with the UN system to create incentives for governments to strengthen NHRIs.