The promulgation of model laws—exemplary statutes that states can voluntarily choose to adopt—is a prominent strategy that reformers in public health agencies, the legal academy, and non governmental organizations use to improve US public health law and make it more uniform. This article applies the science and technology studies literature on standardization to the process of model lawmaking to analyze how developers negotiate between alternative forms of expertise and utilize different drafting processes to secure the techno-political legitimacy of their model statutes. Drawing on archival records and interviews with thirty-four experts involved in the development of four model public health laws produced between 1999 and 2007, I show how developers work to satisfy multiple, and, at times, competing, audiences. I observe that developers leveraged forms of legal expertise to secure their model laws’ technical legitimacy and emphasized their objectivity, representativeness, and flexibility to promote their political legitimacy. Comparing the four model laws across several indicia of legitimacy, I find that the developers experienced varying degrees of success. This study contributes to the socio legal scholarship on model laws by revealing how they are able to achieve legitimacy, albeit fragmented, even in the context of scientific uncertainty.