10 U.S.C. § 18234

No expenditures or contribution may be made for a facility under section 18233 of this title , unless the Secretary of Defense determines that— (1) the number of units of the reserve components of the armed forces located or to be located in the area within which the facility is to be provided is not and will not be larger than the number that can reasonably be expected to be maintained at authorized strength, considering the number of persons living in the area who are qualified for membership in those reserve units; and (2) the plan under which the facility is to be provided makes provision for the greatest practicable use of the facility jointly by units of two or more of those components.