Documentary maker Corey Wascinski looks at illegal immigration, focusing on the title activists who guard the U.S.-Mexico border. The opening passages suggest field notes for an unwritten Cormac McCarthy novel, as self-proclaimed “crusty old men” describe the rigors of their unsolicited patrols. Cowboys misplaced in time, they speak proudly of their self-imposed isolation and peril, which Wascinski reflects in some fine images of the Arizona desert. Unfortunately he undermines this material with amateurishly shot scenes of migrant rights rallies and of middle-class racists taunting Mexicans in San Diego; these episodes do little but reaffirm how polarizing the issue is. What begins in the vicinity of cinema soon descends to the level of local TV coverage, though the Minutemen themselves stand tall in the imagination. 83 min. —Ben Sachs