a Member of Congress to the Washington Metropolitan Area. (2) Waivers in case of emergency or threats to security The head of an executive agency may waive the application of subsection (a) to travel by an employee of the agency if the head of the agency determines that travel by the employee is necessary to respond to a threat to national security, a significant law enforcement event, or a natural disaster or other similar emergency. (c) Period described The period described in this paragraph is the period that— (1) begins on the 31st consecutive day on which appropriations and funds are made available pursuant to section 1311 of title 31, United States Code (as added by section 2(a))