Tijuana -- San Diego State is a U.S. university with one foot in Mexico. But studies south of the border are on hold after California State University administrators prohibited all university-sponsored activities in this sprawling city. Drug war violence, they say, poses a threat to visitors. Many students think the only thing threatened now is their education. "This ban is devastating.… It puts an end to my research here," said Alaina Gallegos, 29, a student of Latin American studies and public health. Such students as Gallegos, along with faculty and Baja California state officials, are mounting a campaign to overturn...