Officials authorized to act as governor pursuant to this Act and emergency interim successors are empowered to exercise the powers and discharge the duties of an office as herein authorized only after an attack upon the United States, as defined herein, has occurred; except that emergency interim successors for local offices are also empowered to exercise the powers and discharge the duties of offices as authorized in Sections 6 and 7 during a disaster within a political subdivision. The legislature may at any time terminate the authority of such emergency interim successors to exercise the powers and discharge the duties of office as herein provided.