On a chilly South Texas afternoon, 20 federal and state lawmen sporting flak jackets and semiautomatic rifles descended on a secluded bungalow near the Rio Grande in Starr County. They arrested three men who were darting out the back. Inside, the cops found giant trash bags of marijuana. Suddenly the ceiling gave way from the weight of other people hiding in the bungalow. All told, 14 Mexicans were charged with drug possession, and 2,000 lbs. of dope were confiscated.
The raid last February was one of a mounting number of armed encounters along the Texas border between lawmen and well-organized, well-financed...