When—

(1) 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

(2) 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;

the Secretary of Defense, under regulations prescribed by the President, shall enter into an agreement with the State within 120 days of a request for agreement from the proper State official. The agreement shall provide that the Department of Defense shall comply with the requirements of State statute as to the individuals named by paragraph (2) of this section who are eligible for membership in the State employee retirement system. The disbursing officials paying these individuals shall withhold and pay to the State employee retirement system or to the person or organization designated by State authorities to receive sums withheld for the program the employee contributions for these individuals. For the purpose of this section, “State” means a State or territory or possession of the United States including the Commonwealth of Puerto Rico.