American Political Science Review

Research Article

Cross-Border Spillover: U.S. Gun Laws and Violence in Mexico


a1 University of Massachusetts Amherst

a2 New York University

a3 New York University


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 U.S. 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 gun seizures after 2004. Second, the magnitude of this effect is contingent on political factors related to Mexico's democratic transition. Killings increased disproportionately in municipios where local elections had become more competitive prior to 2004, with the largest differentials emerging in high narco-trafficking areas. Our findings suggest that competition undermined informal agreements between drug cartels and entrenched local governments, highlighting the role of political conditions in mediating the gun-crime relationship.


c1 Arindrajit Dube is Assistant Professor of Economics, Department of Economics, University of Massachusetts Amherst, Thompson Hall. Amherst, MA 01003 (

c2 Oeindrila Dube is Assistant Professor of Politics and Economics, Department of Politics, New York University, 19 West 4th Street, New York, NY 10012-1119 (

c3 Omar García-Ponce is a Ph.D. candidate, Department of Politics, New York University, 19 West 4th Street, New York, NY 10012-1119 (


  We are especially grateful to Sanford Gordon for numerous discussions, and also thank Joshua Angrist, Eli Berman, Michael Clemens, William Easterly, Jon Eguia, Macartan Humphreys, Brian Knight, David Laitin, John Lott, Jens Ludwig, Sendhil Mullainathan, Emily Owens, Debraj Ray, Peter Rosendorff, Alexandra Scacco, Jake Shapiro, and David Stasavage as well as participants at the Stanford Conference on Mexican Security, NBER Crime Working Group, Columbia CSDS, IAE Conflict Concentration, ESOP Political Economy of Conflict Conference, LACEA-AL CAPONE, Oxford OxCarre Seminar, LSE Political Economy Seminar, Universidad Javeriana, El Colegio de México CEE, and Yale MacMillan Center-CSAP Workshop for providing useful comments.