Presidents Lyndon Johnson and Richard Nixon dramatically expanded the federal government's domestic security apparatus to cope with social unrest that rocked their administrations. By the mid-1970s, the Justice Department and Army maintained some 400 databanks containing nearly 200 million files on supposedly subversive individuals and organizations.

Katherine Scott chronicles the subsequent public response to that government action: a determined citizens' movement to rein in the state. She details the efforts of a group of unheralded heroes who battled to reinvigorate judicial,...