53 Pa. Stat. § 881.121
Notwithstanding any other provision of this act, a domestic relations order may provide for an irrevocable survivor annuitant. A domestic relations order requiring the designation of an irrevocable survivor annuitant shall be deemed to be one that requires a member to designate an alternate payee as a survivor annuitant and that prohibits the removal or change of that survivor annuitant without approval of a court of competent jurisdiction, except by operation of law. A domestic relations order subject to this section may be certified as an approved domestic relations order by the secretary of the board or the secretary's designated representative, in which case the irrevocable survivor annuitant ordered by the court may not be changed by the member without approval of the court. A person ineligible to be designated as a survivor annuitant may not be designated an irrevocable survivor annuitant.
53 P.S. § 881.121