5 U.S.C. § 5518: Deductions for State retirement systems; National Guard employees

a State statute provides for the payment of employee contributions to a State employee retirement system or to a State sponsored plan providing retirement, disability, or death benefits, by withholding sums from the pay of State employees and making returns of the sums withheld to State authorities or to the person or organization designated by State authorities to receive sums withheld for the program; and individuals employed by the Army National Guard and the Air National Guard, except employees of the National Guard Bureau, are eligible for membership in a State employee retirement system or other State sponsored plan;