From my way back days, I thought only the IRS could put a lien on a participant's benefit. But maybe that was a lien and not an in-service distribution to satisfy some IRS tax/penalty... ?
[i am not a lawyer, but] If it was neither an IRS tax lien or a court order determined by the plan administrator to be a QDRO (which would never be the case for a court order to discharge a debt owed to a non-dependent), the plan administrator has a fiduciary obligation to reject the court order. So if the plan complied and paid it out, the participant would have what would probably have been a sound cause of action against the plan administrator. If the participant owed somebody some money but had no funds other than those held by the plan, the creditor is plain out of luck until and unless the participant directs the plan administrator to pay the money to the participant. The money can never be paid directly to the creditor.