Characterizes variation in the design, implementation, and enforcement of comprehensive background check and purchaser licensing (permit-to-purchase) policies across states, from 1980 through 2019. Design, implementation, and enforcement elements were chosen based on their hypothesized ability to influence the effectiveness of comprehensive background check and purchaser licensing policies. Design elements include policy characteristics such as whether the background check is completed at the point of sale or during a permitting process, the ease of completing the permitting process, and whether and which additional firearm prohibitions the state includes (e.g. violent misdemeanor conviction). Implementation elements include the quality and completeness of prohibiting records and the ways in which these data are shared across agencies. Enforcement elements include the presence and severity of penalties for violating these laws and the presence of complementary laws such as anti-straw purchasing policies.