5 ILCS 195/1
Whenever, due to an emergency resulting from the effects of enemy attack, or the anticipated effects of a threatened enemy attack, it becomes imprudent, inexpedient or impossible to conduct the affairs of State Government at the normal location of the seat thereof in the City of Springfield, in the County, Sangamon, the Governor shall, as often as the exigencies of the situation require, by proclamation, declare an emergency temporary location, or locations, for the seat of government at such place, or places, within or without this State as he may deem advisable under the circumstances, and shall take such action and issue such orders as may be necessary for an orderly transition of the affairs of State Government to such emergency temporary location, or locations. Such emergency temporary location, or locations, shall remain as the seat of government until the General Assembly shall by law establish a new location, or locations, or until the emergency is declared to be ended by the Governor and the seat of government is returned to its normal location.
5 ILCS 195/1