Tracking of infectious diseases is a public health core function essential to disease prevention and control. Each state mandates reporting of certain infectious diseases to public health authorities. These laws vary by state, and the variation could affect the ability to collect critical information. The 2009 H1N1 influenza pandemic served as a case study to examine the legal authority in the 50 states; Washington, DC; and New York City for mandatory infectious disease reporting, particularly for influenza and new or emerging infectious diseases. Our study showed reporting laws to be generally present and functioning well; nevertheless, jurisdictions should be mindful of their mandated parameters and review the robustness of their laws before they face a new or emerging disease outbreak.