Matt Singer’s review published on Letterboxd:
On paper, a structure that compares vigilante groups on either side of the U.S.-Mexico border makes a lot of sense. But in practice, the scenes in Mexico (where a vigilante group called the Autodefensas springs up to protect locals from a drug cartel that is intimidating and murdering the populace) are a lot more compelling than the ones in America (where a bunch of right-wingers patrol the border to little effect). It feels like director Matthew Heineman recognized that too; after early scenes establish a back-and-forth structure, the Americans fade into the background while the leader of the Autodefensas, Dr. José Mireles, becomes the main protagonist. Massive respect to Heineman for his fearless work in the field, but if he'd applied an equally bold approach in the editing room and cut the U.S. scenes entirely, he'd have an even stronger documentary.