Is Mexico's Military Out of Control?

Mexico's drug cartels are so powerful that local and national police -- notorious for corruption -- have been replaced by Marines and soldiers. In the name of restoring law and order, they're doing what they've been trained to do, and killing has become more common than arrest and prosecution. Civilians are among the victims; the UN and human rights groups have expressed alarm, but two successive presidents claim there's no alternative to the armed forces. We hear about a growing constitutional crisis -- financed in part by American military assistance.