24 Pa. C.S. § 8533.2
Notwithstanding any other provision of this part, a domestic relations order may provide for an irrevocable beneficiary. A domestic relations order requiring the nomination of an irrevocable beneficiary shall be deemed to be one that requires a member or participant to nominate an alternate payee as a beneficiary and that prohibits the removal or change of that beneficiary without approval of a court of competent jurisdiction, except by operation of law. Such a domestic relations order may be certified as an approved domestic relations order by the secretary of the board, or his designated representative, after the member or participant makes such nomination, in which case the irrevocable beneficiary so ordered by the court cannot be changed by the member or participant without approval by the court.
24 Pa.C.S. § 8533.2