Secondhand cannabis smoke, like secondhand tobacco smoke, creates unhealthy indoor air quality. Ventilation and engineering techniques cannot reduce this pollution to healthy levels, and complete smoke-free policies are the only way to provide healthy indoor environments. Even so, multiple state and local governments have begun to allow indoor smoking of cannabis in businesses. A systematic search of Lexis Advance, NewsBank, and government websites for U.S. state and local laws passed between November 6, 2012 and June 10, 2020 that permit and regulate onsite cannabis consumption businesses was conducted in February-July 2020. In total, 6 of 11 states and the District of Columbia that legalized adult-use cannabis as of June 10, 2020 allowed onsite consumption and ≥56 localities within these 6 states allowed onsite cannabis consumption. Only 9% (5/56) of localities ban indoor smoking in these businesses; 23% (13/56) require indoor smoking to occur in physically isolated rooms. Other common local legal requirements address onsite odor control, ventilation/filtration, and building location. The majority of the localities that allow onsite cannabis consumption do not explicitly prohibit smoking or vaping inside. Policymakers should be made aware that ventilation and other engineering interventions cannot fully protect workers and patrons. Health authorities and local leaders should educate policymakers on the science of secondhand smoke remediation and advocate for the same standards for secondhand cannabis smoking and vaping that apply to tobacco, particularly because other modes of cannabis administration do not pollute the air.