U.S. Homeland Security Secretary Janet Napolitano on Monday warned drug cartels that any attempt to bringing their violent tactics across the border would produce a powerful reaction. “Today I say to the cartels: don't even think about bringing your violence and tactics across this border,” Napolitano said at the University of Texas at El Paso. “You will be met by an overwhelming response. And we are going to continue to work with our partners in Mexico to dismantle and defeat you.”