22 CFR §19.7-6

1. (a)A spousal agreement may be revised or voided by agreement of the parties (by filing a new agreement under this section) at any time prior to the last day for filing an agreement determined in accordance with § 19.7-2 or § 19.7-3, except spousal agreements for additional survivor annuities are irrevocable. After the last day for filing a particular agreement, such agreement is irrevocable.
2. (b)A valid spousal agreement entered into subsequent to the issuance of a court order affecting the same parties will override the court order, and shall govern payments from the Fund.
3. (c)A spousal agreement may not override a previous spousal agreement involving the same principal but a different spouse or former spouse without agreement of such spouse or former spouse.