It appears the US is still in the Continuity of Government status invoked as a result of 9/11.
There is considerable confusion between the use of extra-constitutional powers and "martial law" in an emergency situation, and Continuity of Government as such. Continuity of Government properly refers to processes, systems, and infrastructure whereby Government control and communications can be maintained. They involve communications systems, operating procedures, delegation of responsibility, and emergency accommodation- including bunkers.
The use of unusual powers in an emergency- whether legal or illegal- are not Continuity of Government so much as restraints on legal and constitutional rights. Historically many governments and leaders have used a disaster or attack as an excuse to assume illegal and draconian powers.
Above article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Continuity of government".