To what extent, and under what conditions, does access to arms fuel violent crime? To
answer this question, we exploit a unique natural experiment: the 2004 expiration of the US
Federal Assault Weapons Ban exerted a spillover on gun supply in Mexican municipios near
Texas, Arizona, and New Mexico, but not near California, which retained a pre-existing state-
level ban. We find first that Mexican municipios located closer to the non-California border
states experienced differential increases in homicides, gun-related homicides, and crime …