Earlier this month, when Mexico released a drug kingpin serving time for the hideous murder of a U.S. Drug Enforcement Administration agent, Americans were reminded of the weak laws and widening violence south of the border. Indeed, the staccato of assault weapons vies with mariachi music as the great Mexican cliché in the gringo mind. But a lot of those guns are sold by “legitimate” dealers in the United States. President Bill Clinton signed a treaty to curb cross-border weapons traffic back in 1997, but a Senate in thrall to the gun lobby has never ratified it. The Obama administration imposed a rule in border states requiring gun dealers to report sales of more than two semiautomatic rifles to the same person within five days, only to see such sales shift to other states. But more administrative steps can be taken, argues Julia Sweig of the Council on Foreign Relations: the rule in the border states should be extended nationwide; the 1968 “sporting test” banning the import of many military-style assault rifles, thus preventing them from entering the U.S. firearms market, should be applied. Without such measures, the cliché vision of the gringo, seen from Latin America, will be as a merchant of death.