S.D. Codified Laws § 58-14-4.2
The reinsurance agreement may provide that the domiciliary liquidator of an insolvent ceding insurer shall give written notice to the reinsurer of the pendency of a claim against such ceding insurer on the contract reinsured within a reasonable time after such claim is filed in the liquidation proceeding. During the pendency of such claim, any reinsurer may investigate such claim and interpose, at its own expense, in the proceeding where such claim is to be adjudicated any defenses that it deems available to the ceding insurer or its liquidator. Such expense may be filed as a claim against the insolvent ceding insurer as a Class 6 claim pursuant to § 58-29B-124 to the extent of a proportionate share of the benefit that may accrue to the ceding insurer solely as result of the defense undertaken by the reinsurer. If two or more reinsurers are involved in the same claim and a majority in interest elect to interpose a defense to such claim, the expense shall be apportioned in accordance with the terms of the reinsurance agreement as though such expense had been incurred by the ceding insurer.
SDCL 58-14-4.2