Rex 84, short for Readiness Exercise 1984, was an alleged classified "scenario and drill" developed by the United States federal government to suspend the United States Constitution, declare martial law, place military commanders in charge of state and local governments, and detain large numbers of American citizens who are deemed to be "national security threats", in the event that the President declares a "State of National Emergency". The plan states, events causing 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 supposedly written by Lieutenant Colonel Oliver North, who was both National Security Council White House Aide, and NSC liaison to the Federal Emergency Management Agency (FEMA), and John Brinkerhoff, the deputy director of "national preparedness" programs for the 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 an article in CounterSpy.
Transcripts from the Iran-Contra Hearings in 1987 record the following dialogue between Congressman Jack Brooks, Oliver North's attorney Brendan Sullivan and Senator Daniel Inouye, the Democratic Chair of the joint Senate-House Committee:
Congressman Jack Brooks: Colonel North, in your work at the N.S.C. were you not assigned, at one time, to work on plans for the continuity of government in the event of a major disaster?
Brendan Sullivan North's counsel, agitatedly: Mr. Chairman?
Senator Daniel Inouye: I believe that question touches upon a highly sensitive and classified area so may I request that you not touch upon that?
Brooks: I was particularly concerned, Mr. Chairman, because I read in Miami papers, and several others, that there had been a plan developed, by that same agency, a contingency plan in the event of emergency, that would suspend the American constitution. And I was deeply concerned about it and wondered if that was an area in which he had worked. I believe that it was and I wanted to get his confirmation.
Inouye: May I most respectfully request that that matter not be touched upon at this stage. If we wish to get into this, I'm certain arrangements can be made for an executive session.
Exercises similar to Rex 84 have happened in the past. 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.