22 U.S.C. § 4071k

A spousal agreement is any written agreement (properly authenticated as determined by the Secretary of State) between a participant or former participant and his or her spouse or former spouse on file with the Secretary of State. A spousal agreement shall be consistent with the terms of this chapter and applicable regulations and, if executed at the time a participant or former participant is currently married, shall be approved by such current spouse. It may be used to fix the level of benefits payable under this part to a spouse or former spouse.