of nonessential vehicle purchase For each of fiscal years 2017 through 2021, each Executive agency may not obligate more than the dollar amount determined under subsection (a)(5) for the Executive agency to purchase or lease civilian vehicles. (c) Sharing The Administrator of General Services shall ensure that an Executive agency may share excess or unused vehicles with another Executive agency that may need temporary or long-term use of additional vehicles through the Federal Fleet Management System. (d) National security exception The limits on the purchase and procurement of vehicles under this section shall not apply to the purchase or procurement of any vehicle that has been determined by the President to be essential for reasons of national security. (e) Definitions In this section: (1) Civilian vehicle The term civilian vehicle means a vehicle that is not used for purposes of military combat, the training or deployment of members of the Armed Forces, or such other uses as determined by the Director of the Office of Management and Budget, in consultation with the Administrator of General Services. (2) Executive agency The term Executive agency has the meaning given that term under section 105 of title 5, United States Code. 5. United States Enrichment Corporation Fund (a) Rescission Subject to subsection (b), all unobligated amounts in the United States Enrichment Corporation Fund are permanently rescinded. (b) Exclusions from rescission The rescission under subsection (a) shall not apply to amounts that were designated by Congress as an emergency requirement pursuant to section 251(b)(2)(A)(i) of the Balanced Budget and Emergency Deficit Control Act of 1985 ( 2 U.S.C. 901(b)(2)(A)(i) ).