Much of the talk about the U.S.-Mexico relationship these days centers on the flow of illegal guns south over the border. Fair enough, and long overdue. American weapons, easily bought thanks to woefully lax gun-control laws, are winding up in the arsenal of Mexican drug cartels, who are murdering thousands and destabilizing our southern neighbor. The havoc is spilling over into our border states. But let's not neglect an equally dangerous trend in firearm trafficking - namely, the flow of illegal weapons from America's Southern states north, especially to big cities like New York. As crime has declined in some...
