The short answer is “it depends.”
A domestic partner dissolution may divide a state public plan with a domestic relations order. However, a private employer plan which includes any union plans and any federal plans (e.g., federal employees or military) will not accept or implement a QDRO.
Bottom line: For domestic partnerships, direct payments to a former spouse from a retirement plan can be paid from a state public plan but cannot be paid from any private employer plan or federal plan.
What are options for domestic partners? Many times, the parties will equalize and offset the retirement asset against some other asset if the plan cannot be divided with a QDRO. Or the parties may choose to retain counsel to draft a pay-over order to pay the non-member a share of the retirement asset at the time it is paid to the member. Note that pay-over orders can be difficult for both parties due to enforcement and tax issues.
For retirement benefit that cannot be divided with a QDRO, settling the matter in some way with an equalization or offset is often the best option.