Arizona's Support Our Law Enforcement and Safe Neighborhoods Act, signed into law in April 2010, is already adversely affecting public health in the state. Our findings from a study on childhood obesity in Flagstaff suggest that the law changed health-seeking behaviors of residents of a predominantly Latino neighborhood by increasing fear, limiting residents' mobility, and diminishing trust of officials. These changes could exacerbate barriers to healthy living, limit access to care, and affect the overall safety of the neighborhood. Documentation of the on-the-ground impact of Arizona's law and similar state-level immigration policies is urgently needed. To inform effective policymaking, such research must be community engaged and include safety measures beyond the usual protocols.