His award winning book, Border Contraband: A History of Smuggling across the Rio Grande, was published with the University of Texas Press. Recently he served as the Visiting Scholar at the Center for Mexican American Studies at the University of Houston where he designed and taught a course on smuggling in the U.S.-Mexico borderlands. Díaz teaches courses in U.S., Borderlands, and Mexican American history. His research is informed by investigations in Mexican and U.S. archives as well as a lifetime of living on the border.