In 1984, the Rex-84 readiness exercise program was conducted by 34 federal departments and agencies, reportedly as an exercise to handle an influx of illegal aliens crossing the Mexican/U.S. border. Brought to Americans' attention during the Iran-contra hearings, the exercise, which was conducted alongside another drill, "Night Train 84," also tested military readiness to round up and detain citizens in case of massive civil unrest.
None of that ever happened, of course, and in many respects, it seems silly to even mention it. After all, other Reagan-era initiatives, like the Armageddon exercises Dick Cheney and Donald Rumsfeld participated in, are far more interesting. Then, too, despite a brief moment of sunlight in the 1970s (when Congress, according to former President and CIA director George H.W. Bush, "unleashed a bunch of untutored little jerks out there"), emergency detention plans had been in place since the 1950s, without incident. Americans have not been herded into camps since World War II, so why worry about it now?
More in link below
http://www.buzzflash.com/farrell/06/02/far06003.html