The plan stated that events that might cause such a declaration would be widespread U.S. opposition to a U.S. military invasion abroad, such as if the United States were to directly invade Central America.
To combat what the government perceived as "subversive activities", the plan also authorized the military to direct ordered movements of civilian populations at state and regional levels.
Rex 84 was written by Lieutenant Colonel Oliver North, who was both the NSC White House Aide and NSC liaison to FEMA, and John Brinkerhoff, the deputy director of "national preparedness" programs for FEMA.
They patterned the plan on a 1970 report written by FEMA chief Louis Giuffrida, at the Army War College, which proposed the detention of up to 21 million "American Negroes", if there were a black militant uprising in the United States.
Existence of a master military contingency plan (of which REX-84 was a part), "Garden Plot" and a similar earlier exercise, "Lantern Spike" were originally revealed by journalist Ron Ridenhour, who summarized his findings in "Garden Plot and the New Action Army."
Rex 84 was publicly mentioned during the Iran-Contra Hearings in 1987.
Exercises similar to Rex 84 happen regularly. For example, from 1967 to 1971 the FBI kept a list of over 100,000 persons to be rounded up as subversive, dubbed the "ADEX" list.
The basic facts about Rex 84 and other contingency planning readiness exercises—and the potential threat they pose to civil liberties if fully implemented in a real operation—are taken seriously by scholars and civil libertarians.
