The prohibition in 223.7303 does not apply to--
(a) Legacy systems and their related parts, subsystems, and components that already contain hexavalent chromium. However, alternatives to hexavalent chromium shall be considered by the appropriate official during system modifications, follow-on procurements of legacy systems, or maintenance procedure updates; and
(b) Additional sustainment related contracts (e.g., parts, services) for a system in which use of hexavalent chromium was previously approved.